Fix //tests/legacy/examples/cgo:cgo_lib_test on M1 Macs

[fmeum]

The CPU config setting didn't match for M1 Macs, which are darwin_arm64.
Instead, use a more modern @platforms condition for the special casing.

We should ultimately fix the underlying issue with linking on macOS
instead.

[sluongng]

master ~/work/misc/rules_go> git diff
diff --git a/tests/legacy/examples/cgo/cc_dependency/BUILD.bazel b/tests/legacy/examples/cgo/cc_dependency/BUILD.bazel
index bace2050..f0eee7dd 100644
--- a/tests/legacy/examples/cgo/cc_dependency/BUILD.bazel
+++ b/tests/legacy/examples/cgo/cc_dependency/BUILD.bazel
@@ -1,8 +1,3 @@
-config_setting(
-    name = "darwin",
-    values = {"cpu": "darwin"},
-)
-
 cc_library(
     name = "version",
     srcs = ["cxx_version.cc"],
@@ -12,7 +7,7 @@ cc_library(
     # TODO(yugui) Support darwin too and remove this workaround.
     # See also comments in cxx_version.cc.
     deps = select({
-        ":darwin": [],
+        "@platforms//os:macos": [],
         "//conditions:default": [":c_version_import"],
     }),
 )
master ~/work/misc/rules_go> bazel test tests/legacy/examples/cgo:cgo_lib_test --verbose_failures --test_output=errors --sandbox_debug
INFO: Invocation ID: 5e6bac6d-a748-4896-b048-b4394427cd16
DEBUG: /private/var/tmp/_bazel_sngoc/2a28a4eea77aca2bd34246f26b53d6f4/external/bazel_toolchains/rules/rbe_repo/version_check.bzl:68:14:
Current running Bazel is ahead of bazel-toolchains repo. Please update your pin to bazel-toolchains repo in your WORKSPACE file.
DEBUG: /private/var/tmp/_bazel_sngoc/2a28a4eea77aca2bd34246f26b53d6f4/external/bazel_toolchains/rules/rbe_repo/checked_in.bzl:125:14: buildkite_config not using checked in configs; Bazel version 5.2.0 was picked/selected but no checked in config was found in map {"0.20.0": ["8.0.0"], "0.21.0": ["8.0.0"], "0.22.0": ["8.0.0", "9.0.0"], "0.23.0": ["8.0.0", "9.0.0"], "0.23.1": ["8.0.0", "9.0.0"], "0.23.2": ["9.0.0"], "0.24.0": ["9.0.0"], "0.24.1": ["9.0.0"], "0.25.0": ["9.0.0"], "0.25.1": ["9.0.0"], "0.25.2": ["9.0.0"], "0.26.0": ["9.0.0"], "0.26.1": ["9.0.0"], "0.27.0": ["9.0.0"], "0.27.1": ["9.0.0"], "0.28.0": ["9.0.0"], "0.28.1": ["9.0.0"], "0.29.0": ["9.0.0"], "0.29.1": ["9.0.0", "10.0.0"], "1.0.0": ["9.0.0", "10.0.0"], "1.0.1": ["10.0.0"], "1.1.0": ["10.0.0"], "1.2.0": ["10.0.0"], "1.2.1": ["10.0.0"], "2.0.0": ["10.0.0"], "2.1.0": ["10.0.0"], "2.1.1": ["10.0.0", "11.0.0"], "2.2.0": ["11.0.0"], "3.0.0": ["11.0.0"], "3.1.0": ["11.0.0"], "3.2.0": ["11.0.0"], "3.3.0": ["11.0.0"], "3.3.1": ["11.0.0"], "3.4.1": ["11.0.0"], "3.5.0": ["11.0.0"], "3.5.1": ["11.0.0"], "3.6.0": ["11.0.0"], "3.7.0": ["11.0.0"], "3.7.1": ["11.0.0"], "3.7.2": ["11.0.0"], "4.0.0": ["11.0.0"]}
INFO: Analyzed target //tests/legacy/examples/cgo:cgo_lib_test (0 packages loaded, 0 targets configured).
INFO: Found 1 test target...
Target //tests/legacy/examples/cgo:cgo_lib_test up-to-date:
  bazel-bin/tests/legacy/examples/cgo/cgo_lib_test_/cgo_lib_test
INFO: Elapsed time: 0.697s, Critical Path: 0.00s
INFO: 1 process: 1 internal.
INFO: Build completed successfully, 1 total action
//tests/legacy/examples/cgo:cgo_lib_test                        (cached) PASSED in 2.9s

INFO: Build completed successfully, 1 total action

It worked 🙌
Nicely done!