Switch everything to platforms

This patch switches the codebase over from using the "cpu"
mechanism to using bazel platforms. See
https://docs.bazel.build/versions/master/platforms.html for some more
information.

Most of the substantial changes are in //tools. Instead of using
`cc_toolchain_suite` rules, we now use regular `toolchain` rules that
are registered in the WORKSPACE. That also means that bazel now uses
the target platform to select the compiler.

All --cpu=* arguments should now be --config=* arguments. For example,
`--cpu=roborio` should now be `--config=roborio`. The CI script and
all documentation has been updated to reflect that.

The remainder of the changes revolve around tagging all targets with
`target_compatible_with`.  The old mechanism allowed us to specify
repo-wide defaults. The new mechanism does not. That means every
target that didn't have any compatibility specified, now requires
compatibility with `@platforms//os:linux`.

I used buildozer for the vast majority of `target_compatible_with`
changes. buildozer automatically buildifies any BUILD files it
touches. That means this patch also contains a few non-functional
changes that I was too lazy to remove.

Change-Id: I66d6e6ad9161520ee397597cdb492585820a3acd
diff --git a/y2020/control_loops/BUILD b/y2020/control_loops/BUILD
index c0aa1ee..75ca8eb 100644
--- a/y2020/control_loops/BUILD
+++ b/y2020/control_loops/BUILD
@@ -1,6 +1,7 @@
 py_library(
     name = "python_init",
     srcs = ["__init__.py"],
+    target_compatible_with = ["@platforms//os:linux"],
     visibility = ["//visibility:public"],
     deps = ["//y2020:python_init"],
 )
diff --git a/y2020/control_loops/drivetrain/BUILD b/y2020/control_loops/drivetrain/BUILD
index 7e2ba18..490b1e7 100644
--- a/y2020/control_loops/drivetrain/BUILD
+++ b/y2020/control_loops/drivetrain/BUILD
@@ -11,6 +11,7 @@
         "kalman_drivetrain_motor_plant.cc",
     ],
     cmd = "$(location //y2020/control_loops/python:drivetrain) $(OUTS)",
+    target_compatible_with = ["@platforms//os:linux"],
     tools = [
         "//y2020/control_loops/python:drivetrain",
     ],
@@ -27,6 +28,7 @@
         "hybrid_velocity_drivetrain.cc",
     ],
     cmd = "$(location //y2020/control_loops/python:polydrivetrain) $(OUTS)",
+    target_compatible_with = ["@platforms//os:linux"],
     tools = [
         "//y2020/control_loops/python:polydrivetrain",
     ],
@@ -46,6 +48,7 @@
         "kalman_drivetrain_motor_plant.h",
         "polydrivetrain_dog_motor_plant.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     visibility = ["//visibility:public"],
     deps = [
         "//frc971/control_loops:hybrid_state_feedback_loop",
@@ -57,6 +60,7 @@
     name = "localizer",
     srcs = ["localizer.cc"],
     hdrs = ["localizer.h"],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         "//aos/containers:ring_buffer",
         "//aos/network:message_bridge_server_fbs",
@@ -77,6 +81,7 @@
     hdrs = [
         "drivetrain_base.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     visibility = ["//visibility:public"],
     deps = [
         ":polydrivetrain_plants",
@@ -90,6 +95,7 @@
     srcs = [
         "drivetrain_main.cc",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     visibility = ["//visibility:public"],
     deps = [
         ":drivetrain_base",
@@ -103,6 +109,7 @@
 aos_config(
     name = "simulation_config",
     src = "drivetrain_simulation_config.json",
+    target_compatible_with = ["@platforms//os:linux"],
     visibility = ["//visibility:public"],
     deps = [
         "//frc971/control_loops/drivetrain:simulation_channels",
@@ -113,6 +120,7 @@
 aos_config(
     name = "replay_config",
     src = "drivetrain_replay_config.json",
+    target_compatible_with = ["@platforms//os:linux"],
     visibility = ["//visibility:public"],
     deps = [
         "//y2020:config",
@@ -123,6 +131,7 @@
     name = "localizer_test",
     srcs = ["localizer_test.cc"],
     data = [":simulation_config"],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":drivetrain_base",
         ":localizer",
@@ -143,6 +152,7 @@
         ":replay_config",
         "@drivetrain_replay//file:spinning_wheels_while_still.bfbs",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":drivetrain_base",
         "//aos:configuration",
@@ -161,6 +171,7 @@
     name = "drivetrain_replay",
     srcs = ["drivetrain_replay.cc"],
     data = ["//y2020:config"],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":drivetrain_base",
         ":localizer",
diff --git a/y2020/control_loops/python/BUILD b/y2020/control_loops/python/BUILD
index e218571..34d49cb 100644
--- a/y2020/control_loops/python/BUILD
+++ b/y2020/control_loops/python/BUILD
@@ -6,7 +6,7 @@
         "drivetrain.py",
     ],
     legacy_create_init = False,
-    restricted_to = ["//tools:k8"],
+    target_compatible_with = ["@platforms//cpu:x86_64"],
     deps = [
         ":python_init",
         "//external:python-gflags",
@@ -22,7 +22,7 @@
         "polydrivetrain.py",
     ],
     legacy_create_init = False,
-    restricted_to = ["//tools:k8"],
+    target_compatible_with = ["@platforms//cpu:x86_64"],
     deps = [
         ":python_init",
         "//external:python-gflags",
@@ -37,7 +37,7 @@
         "drivetrain.py",
         "polydrivetrain.py",
     ],
-    restricted_to = ["//tools:k8"],
+    target_compatible_with = ["@platforms//cpu:x86_64"],
     visibility = ["//visibility:public"],
     deps = [
         ":python_init",
@@ -55,7 +55,7 @@
         "hood.py",
     ],
     legacy_create_init = False,
-    restricted_to = ["//tools:k8"],
+    target_compatible_with = ["@platforms//cpu:x86_64"],
     deps = [
         ":python_init",
         "//external:python-gflags",
@@ -71,7 +71,7 @@
         "intake.py",
     ],
     legacy_create_init = False,
-    restricted_to = ["//tools:k8"],
+    target_compatible_with = ["@platforms//cpu:x86_64"],
     deps = [
         ":python_init",
         "//external:python-gflags",
@@ -87,7 +87,7 @@
         "turret.py",
     ],
     legacy_create_init = False,
-    restricted_to = ["//tools:k8"],
+    target_compatible_with = ["@platforms//cpu:x86_64"],
     deps = [
         ":python_init",
         "//external:python-gflags",
@@ -103,7 +103,7 @@
         "control_panel.py",
     ],
     legacy_create_init = False,
-    restricted_to = ["//tools:k8"],
+    target_compatible_with = ["@platforms//cpu:x86_64"],
     deps = [
         ":python_init",
         "//external:python-gflags",
@@ -118,7 +118,7 @@
     srcs = [
         "flywheel.py",
     ],
-    restricted_to = ["//tools:k8"],
+    target_compatible_with = ["@platforms//cpu:x86_64"],
     deps = [
         "//frc971/control_loops/python:controls",
         "@matplotlib_repo//:matplotlib2.7",
@@ -131,7 +131,7 @@
         "accelerator.py",
     ],
     legacy_create_init = False,
-    restricted_to = ["//tools:k8"],
+    target_compatible_with = ["@platforms//cpu:x86_64"],
     deps = [
         ":flywheel",
         ":python_init",
@@ -146,7 +146,7 @@
         "finisher.py",
     ],
     legacy_create_init = False,
-    restricted_to = ["//tools:k8"],
+    target_compatible_with = ["@platforms//cpu:x86_64"],
     deps = [
         ":flywheel",
         ":python_init",
@@ -158,6 +158,7 @@
 py_library(
     name = "python_init",
     srcs = ["__init__.py"],
+    target_compatible_with = ["@platforms//os:linux"],
     visibility = ["//visibility:public"],
     deps = ["//y2020/control_loops:python_init"],
 )
diff --git a/y2020/control_loops/superstructure/BUILD b/y2020/control_loops/superstructure/BUILD
index e97fb12..d659920 100644
--- a/y2020/control_loops/superstructure/BUILD
+++ b/y2020/control_loops/superstructure/BUILD
@@ -12,6 +12,7 @@
         "//frc971/control_loops:control_loops_fbs_includes",
         "//frc971/control_loops:profiled_subsystem_fbs_includes",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
 )
 
 flatbuffer_cc_library(
@@ -20,6 +21,7 @@
         "superstructure_output.fbs",
     ],
     gen_reflections = 1,
+    target_compatible_with = ["@platforms//os:linux"],
 )
 
 flatbuffer_cc_library(
@@ -32,6 +34,7 @@
         "//frc971/control_loops:control_loops_fbs_includes",
         "//frc971/control_loops:profiled_subsystem_fbs_includes",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
 )
 
 flatbuffer_cc_library(
@@ -44,6 +47,7 @@
         "//frc971/control_loops:control_loops_fbs_includes",
         "//frc971/control_loops:profiled_subsystem_fbs_includes",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
 )
 
 cc_library(
@@ -54,6 +58,7 @@
     hdrs = [
         "superstructure.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":climber",
         ":superstructure_goal_fbs",
@@ -75,6 +80,7 @@
     srcs = [
         "superstructure_main.cc",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":superstructure_lib",
         "//aos:init",
@@ -90,6 +96,7 @@
     data = [
         "//y2020:config",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":superstructure_goal_fbs",
         ":superstructure_lib",
@@ -119,6 +126,7 @@
     hdrs = [
         "climber.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":superstructure_goal_fbs",
         ":superstructure_output_fbs",
diff --git a/y2020/control_loops/superstructure/accelerator/BUILD b/y2020/control_loops/superstructure/accelerator/BUILD
index 30fca08..c2a6717 100644
--- a/y2020/control_loops/superstructure/accelerator/BUILD
+++ b/y2020/control_loops/superstructure/accelerator/BUILD
@@ -1,7 +1,5 @@
 package(default_visibility = ["//visibility:public"])
 
-load("@com_github_google_flatbuffers//:build_defs.bzl", "flatbuffer_cc_library")
-
 genrule(
     name = "genrule_accelerator",
     outs = [
@@ -11,6 +9,7 @@
         "integral_accelerator_plant.cc",
     ],
     cmd = "$(location //y2020/control_loops/python:accelerator) $(OUTS)",
+    target_compatible_with = ["@platforms//os:linux"],
     tools = [
         "//y2020/control_loops/python:accelerator",
     ],
@@ -26,6 +25,7 @@
         "accelerator_plant.h",
         "integral_accelerator_plant.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     visibility = ["//visibility:public"],
     deps = [
         "//frc971/control_loops:hybrid_state_feedback_loop",
diff --git a/y2020/control_loops/superstructure/control_panel/BUILD b/y2020/control_loops/superstructure/control_panel/BUILD
index 75619ca..9f46998 100644
--- a/y2020/control_loops/superstructure/control_panel/BUILD
+++ b/y2020/control_loops/superstructure/control_panel/BUILD
@@ -9,6 +9,7 @@
         "integral_control_panel_plant.cc",
     ],
     cmd = "$(location //y2020/control_loops/python:control_panel) $(OUTS)",
+    target_compatible_with = ["@platforms//os:linux"],
     tools = [
         "//y2020/control_loops/python:control_panel",
     ],
@@ -24,6 +25,7 @@
         "control_panel_plant.h",
         "integral_control_panel_plant.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     visibility = ["//visibility:public"],
     deps = [
         "//frc971/control_loops:hybrid_state_feedback_loop",
diff --git a/y2020/control_loops/superstructure/finisher/BUILD b/y2020/control_loops/superstructure/finisher/BUILD
index 2009886..7a628c8 100644
--- a/y2020/control_loops/superstructure/finisher/BUILD
+++ b/y2020/control_loops/superstructure/finisher/BUILD
@@ -1,7 +1,5 @@
 package(default_visibility = ["//visibility:public"])
 
-load("@com_github_google_flatbuffers//:build_defs.bzl", "flatbuffer_cc_library")
-
 genrule(
     name = "genrule_finisher",
     outs = [
@@ -11,6 +9,7 @@
         "integral_finisher_plant.cc",
     ],
     cmd = "$(location //y2020/control_loops/python:finisher) $(OUTS)",
+    target_compatible_with = ["@platforms//os:linux"],
     tools = [
         "//y2020/control_loops/python:finisher",
     ],
@@ -26,6 +25,7 @@
         "finisher_plant.h",
         "integral_finisher_plant.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     visibility = ["//visibility:public"],
     deps = [
         "//frc971/control_loops:hybrid_state_feedback_loop",
diff --git a/y2020/control_loops/superstructure/hood/BUILD b/y2020/control_loops/superstructure/hood/BUILD
index 6c1a60b..d0e5953 100644
--- a/y2020/control_loops/superstructure/hood/BUILD
+++ b/y2020/control_loops/superstructure/hood/BUILD
@@ -9,6 +9,7 @@
         "integral_hood_plant.cc",
     ],
     cmd = "$(location //y2020/control_loops/python:hood) $(OUTS)",
+    target_compatible_with = ["@platforms//os:linux"],
     tools = [
         "//y2020/control_loops/python:hood",
     ],
@@ -24,6 +25,7 @@
         "hood_plant.h",
         "integral_hood_plant.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     visibility = ["//visibility:public"],
     deps = [
         "//frc971/control_loops:hybrid_state_feedback_loop",
diff --git a/y2020/control_loops/superstructure/intake/BUILD b/y2020/control_loops/superstructure/intake/BUILD
index 2133204..5bb5d7f 100644
--- a/y2020/control_loops/superstructure/intake/BUILD
+++ b/y2020/control_loops/superstructure/intake/BUILD
@@ -9,6 +9,7 @@
         "integral_intake_plant.cc",
     ],
     cmd = "$(location //y2020/control_loops/python:intake) $(OUTS)",
+    target_compatible_with = ["@platforms//os:linux"],
     tools = [
         "//y2020/control_loops/python:intake",
     ],
@@ -24,6 +25,7 @@
         "intake_plant.h",
         "integral_intake_plant.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     visibility = ["//visibility:public"],
     deps = [
         "//frc971/control_loops:hybrid_state_feedback_loop",
diff --git a/y2020/control_loops/superstructure/shooter/BUILD b/y2020/control_loops/superstructure/shooter/BUILD
index fe8a29a..0b65037 100644
--- a/y2020/control_loops/superstructure/shooter/BUILD
+++ b/y2020/control_loops/superstructure/shooter/BUILD
@@ -1,9 +1,8 @@
 package(default_visibility = ["//visibility:public"])
 
-load("@com_github_google_flatbuffers//:build_defs.bzl", "flatbuffer_cc_library")
-
 cc_library(
     name = "shooter_plants",
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         "//frc971/control_loops:state_feedback_loop",
     ],
@@ -17,6 +16,7 @@
     hdrs = [
         "shooter.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":flywheel_controller",
         "//aos/controls:control_loop",
@@ -36,6 +36,7 @@
     hdrs = [
         "flywheel_controller.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         "//aos/controls:control_loop",
         "//frc971/control_loops:profiled_subsystem",
diff --git a/y2020/control_loops/superstructure/turret/BUILD b/y2020/control_loops/superstructure/turret/BUILD
index 010c6fd..3761868 100644
--- a/y2020/control_loops/superstructure/turret/BUILD
+++ b/y2020/control_loops/superstructure/turret/BUILD
@@ -9,6 +9,7 @@
         "integral_turret_plant.cc",
     ],
     cmd = "$(location //y2020/control_loops/python:turret) $(OUTS)",
+    target_compatible_with = ["@platforms//os:linux"],
     tools = [
         "//y2020/control_loops/python:turret",
     ],
@@ -24,6 +25,7 @@
         "integral_turret_plant.h",
         "turret_plant.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     visibility = ["//visibility:public"],
     deps = [
         "//frc971/control_loops:hybrid_state_feedback_loop",
@@ -35,6 +37,7 @@
     name = "aiming",
     srcs = ["aiming.cc"],
     hdrs = ["aiming.h"],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         "//aos:flatbuffers",
         "//frc971/control_loops:control_loops_fbs",
@@ -50,6 +53,7 @@
 cc_test(
     name = "aiming_test",
     srcs = ["aiming_test.cc"],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":aiming",
         "//aos/testing:googletest",