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/y2017/control_loops/superstructure/BUILD b/y2017/control_loops/superstructure/BUILD
index 7107e23..fa835c1 100644
--- a/y2017/control_loops/superstructure/BUILD
+++ b/y2017/control_loops/superstructure/BUILD
@@ -11,6 +11,7 @@
     includes = [
         "//frc971/control_loops:control_loops_fbs_includes",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
 )
 
 flatbuffer_cc_library(
@@ -22,6 +23,7 @@
     includes = [
         "//frc971/control_loops:control_loops_fbs_includes",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
 )
 
 flatbuffer_cc_library(
@@ -34,6 +36,7 @@
         "//frc971/control_loops:control_loops_fbs_includes",
         "//frc971/control_loops:profiled_subsystem_fbs_includes",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
 )
 
 flatbuffer_cc_library(
@@ -42,6 +45,7 @@
         "superstructure_output.fbs",
     ],
     gen_reflections = 1,
+    target_compatible_with = ["@platforms//os:linux"],
 )
 
 cc_library(
@@ -52,6 +56,7 @@
     hdrs = [
         "superstructure.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":superstructure_goal_fbs",
         ":superstructure_output_fbs",
@@ -74,6 +79,7 @@
         "superstructure_lib_test.cc",
     ],
     data = ["//y2017:config"],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":superstructure_goal_fbs",
         ":superstructure_lib",
@@ -98,6 +104,7 @@
     srcs = [
         "superstructure_main.cc",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":superstructure_lib",
         "//aos:init",
@@ -113,6 +120,7 @@
     hdrs = [
         "vision_time_adjuster.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         "//aos/containers:ring_buffer",
         "//frc971/control_loops:control_loops_fbs",
@@ -129,6 +137,7 @@
         "vision_time_adjuster_test.cc",
     ],
     data = ["//y2017:config"],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":vision_time_adjuster",
         "//aos/events:simulated_event_loop",
@@ -143,6 +152,7 @@
     hdrs = [
         "vision_distance_average.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         "//aos/containers:ring_buffer",
         "//aos/time",
@@ -155,6 +165,7 @@
     srcs = [
         "vision_distance_average_test.cc",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":vision_distance_average",
         "//aos:flatbuffers",
diff --git a/y2017/control_loops/superstructure/column/BUILD b/y2017/control_loops/superstructure/column/BUILD
index 63dd98c..e59d1e6 100644
--- a/y2017/control_loops/superstructure/column/BUILD
+++ b/y2017/control_loops/superstructure/column/BUILD
@@ -9,6 +9,7 @@
         "stuck_column_integral_plant.cc",
     ],
     cmd = "$(location //y2017/control_loops/python:column) $(OUTS)",
+    target_compatible_with = ["@platforms//os:linux"],
     tools = [
         "//y2017/control_loops/python:column",
     ],
@@ -26,6 +27,7 @@
         "column_plant.h",
         "stuck_column_integral_plant.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     visibility = ["//visibility:public"],
     deps = [
         "//frc971/control_loops:state_feedback_loop",
@@ -40,6 +42,7 @@
     hdrs = [
         "column.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     visibility = ["//visibility:public"],
     deps = [
         ":column_plants",
@@ -63,6 +66,7 @@
     hdrs = [
         "column_zeroing.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         "//frc971:constants",
         "//frc971/control_loops:profiled_subsystem_fbs",
@@ -79,6 +83,7 @@
     srcs = [
         "column_zeroing_test.cc",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":column_zeroing",
         "//aos/testing:test_shm",
diff --git a/y2017/control_loops/superstructure/hood/BUILD b/y2017/control_loops/superstructure/hood/BUILD
index c3f6ef0..8f162a7 100644
--- a/y2017/control_loops/superstructure/hood/BUILD
+++ b/y2017/control_loops/superstructure/hood/BUILD
@@ -7,6 +7,7 @@
         "hood_integral_plant.cc",
     ],
     cmd = "$(location //y2017/control_loops/python:hood) $(OUTS)",
+    target_compatible_with = ["@platforms//os:linux"],
     tools = [
         "//y2017/control_loops/python:hood",
     ],
@@ -22,6 +23,7 @@
         "hood_integral_plant.h",
         "hood_plant.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     visibility = ["//visibility:public"],
     deps = [
         "//frc971/control_loops:state_feedback_loop",
@@ -36,6 +38,7 @@
     hdrs = [
         "hood.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     visibility = ["//visibility:public"],
     deps = [
         ":hood_plants",
diff --git a/y2017/control_loops/superstructure/intake/BUILD b/y2017/control_loops/superstructure/intake/BUILD
index 43f4927..550c241 100644
--- a/y2017/control_loops/superstructure/intake/BUILD
+++ b/y2017/control_loops/superstructure/intake/BUILD
@@ -7,6 +7,7 @@
         "intake_integral_plant.cc",
     ],
     cmd = "$(location //y2017/control_loops/python:intake) $(OUTS)",
+    target_compatible_with = ["@platforms//os:linux"],
     tools = [
         "//y2017/control_loops/python:intake",
     ],
@@ -22,6 +23,7 @@
         "intake_integral_plant.h",
         "intake_plant.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     visibility = ["//visibility:public"],
     deps = [
         "//frc971/control_loops:state_feedback_loop",
@@ -36,6 +38,7 @@
     hdrs = [
         "intake.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     visibility = ["//visibility:public"],
     deps = [
         ":intake_plants",
diff --git a/y2017/control_loops/superstructure/shooter/BUILD b/y2017/control_loops/superstructure/shooter/BUILD
index d83e34b..49fa341 100644
--- a/y2017/control_loops/superstructure/shooter/BUILD
+++ b/y2017/control_loops/superstructure/shooter/BUILD
@@ -9,6 +9,7 @@
         "shooter_integral_plant.cc",
     ],
     cmd = "$(location //y2017/control_loops/python:shooter) $(OUTS)",
+    target_compatible_with = ["@platforms//os:linux"],
     tools = [
         "//y2017/control_loops/python:shooter",
     ],
@@ -24,6 +25,7 @@
         "shooter_integral_plant.h",
         "shooter_plant.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     visibility = ["//visibility:public"],
     deps = [
         "//frc971/control_loops:hybrid_state_feedback_loop",
@@ -39,6 +41,7 @@
     hdrs = [
         "shooter.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     visibility = ["//visibility:public"],
     deps = [
         ":shooter_plants",