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/aos/util/BUILD b/aos/util/BUILD
index 01be701..f0a65d9 100644
--- a/aos/util/BUILD
+++ b/aos/util/BUILD
@@ -1,13 +1,10 @@
 package(default_visibility = ["//visibility:public"])
 
-load("//tools:environments.bzl", "mcu_cpus")
-
 cc_library(
     name = "bitpacking",
     hdrs = [
         "bitpacking.h",
     ],
-    compatible_with = mcu_cpus,
     visibility = ["//visibility:public"],
     deps = [
         "//third_party/GSL",
@@ -19,6 +16,7 @@
     srcs = [
         "bitpacking_test.cc",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":bitpacking",
         "//aos/testing:googletest",
@@ -30,6 +28,7 @@
     srcs = [
         "trapezoid_profile.py",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":python_init",
     ],
@@ -43,6 +42,7 @@
     hdrs = [
         "run_command.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         "//aos/logging",
     ],
@@ -53,6 +53,7 @@
     srcs = [
         "run_command_test.cc",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":run_command",
         "//aos/logging",
@@ -63,6 +64,7 @@
 cc_library(
     name = "math",
     hdrs = ["math.h"],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         "@org_tuxfamily_eigen//:eigen",
     ],
@@ -71,6 +73,7 @@
 cc_test(
     name = "math_test",
     srcs = ["math_test.cc"],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":math",
         "//aos/testing:googletest",
@@ -82,6 +85,7 @@
     hdrs = [
         "death_test_log_implementation.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         "//aos/logging:implementations",
     ],
@@ -95,6 +99,7 @@
     hdrs = [
         "inet_addr.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         "//aos:byteorder",
         "//aos:network_port",
@@ -109,6 +114,7 @@
     hdrs = [
         "phased_loop.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         "//aos/time",
         "@com_github_google_glog//:glog",
@@ -120,6 +126,7 @@
     hdrs = [
         "log_interval.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         "//aos/logging",
         "//aos/time",
@@ -131,6 +138,7 @@
     hdrs = [
         "string_to_num.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
 )
 
 cc_test(
@@ -138,6 +146,7 @@
     srcs = [
         "string_to_num_test.cc",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":string_to_num",
         "//aos/testing:googletest",
@@ -155,6 +164,7 @@
     linkopts = [
         "-lm",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         "//aos/logging",
         "//aos/time",
@@ -167,6 +177,7 @@
     srcs = [
         "trapezoid_profile_test.cc",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":trapezoid_profile",
         "//aos/testing:googletest",
@@ -181,6 +192,7 @@
     hdrs = [
         "wrapping_counter.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
 )
 
 cc_test(
@@ -188,6 +200,7 @@
     srcs = [
         "wrapping_counter_test.cc",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":wrapping_counter",
         "//aos/testing:googletest",
@@ -199,6 +212,7 @@
     hdrs = [
         "options.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
 )
 
 cc_test(
@@ -206,6 +220,7 @@
     srcs = [
         "options_test.cc",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":options",
         "//aos/testing:googletest",
@@ -217,6 +232,7 @@
     hdrs = [
         "compiler_memory_barrier.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
 )
 
 cc_library(
@@ -224,6 +240,7 @@
     hdrs = [
         "global_factory.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
 )
 
 cc_test(
@@ -231,6 +248,7 @@
     srcs = [
         "global_factory_test.cc",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":global_factory",
         "//aos/testing:googletest",
@@ -242,6 +260,7 @@
     srcs = [
         "phased_loop_test.cc",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":phased_loop",
         "//aos/testing:googletest",
@@ -257,6 +276,7 @@
     hdrs = [
         "file.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         "//aos/scoped:scoped_fd",
         "@com_github_google_glog//:glog",
@@ -270,6 +290,7 @@
     srcs = [
         "file_test.cc",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":file",
         "//aos/testing:googletest",
@@ -279,6 +300,7 @@
 py_library(
     name = "python_init",
     srcs = ["__init__.py"],
+    target_compatible_with = ["@platforms//os:linux"],
     visibility = ["//visibility:public"],
     deps = ["//aos:python_init"],
 )