Make C++ archiving use action_configs instead of hardcoded flags

RELNOTES: Use action_config in crosstool for static library archiving, remove ar_flag.
PiperOrigin-RevId: 157685703
diff --git a/third_party/com/github/bazelbuild/bazel/src/main/protobuf/crosstool_config.proto b/third_party/com/github/bazelbuild/bazel/src/main/protobuf/crosstool_config.proto
index f1123f9..0a16383 100644
--- a/third_party/com/github/bazelbuild/bazel/src/main/protobuf/crosstool_config.proto
+++ b/third_party/com/github/bazelbuild/bazel/src/main/protobuf/crosstool_config.proto
@@ -386,6 +386,7 @@
   repeated string ld_embed_flag = 23;
   // Ar flags for combining object files into archives. If this is not set, it
   // defaults to "rcsD".
+  // TODO(b/37271982): Remove after blaze with ar action_config release
   repeated string ar_flag = 47;
   // Legacy field, ignored by Bazel.
   repeated string ar_thin_archives_flag = 48;