Remove support for thin archives.

RELNOTES: None.
PiperOrigin-RevId: 130938527
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 1144ef9..50a57f3 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
@@ -305,6 +305,7 @@
   // Feature flags.
   // TODO(bazel-team): Sink those into 'Feature' instances.
   optional bool supports_gold_linker = 10 [default = false];
+  // Legacy field, ignored by Bazel.
   optional bool supports_thin_archives = 11 [default = false];
   optional bool supports_start_end_lib = 28 [default = false];
   optional bool supports_interface_shared_objects = 32 [default = false];
@@ -349,8 +350,7 @@
   // Ar flags for combining object files into archives. If this is not set, it
   // defaults to "rcsD".
   repeated string ar_flag = 47;
-  // Ar flags for combining object files into archives when thin_archives is
-  // enabled. If this is not set, it defaults to "rcsDT".
+  // Legacy field, ignored by Bazel.
   repeated string ar_thin_archives_flag = 48;
   // Additional compiler flags that are added for cc_plugin rules of type 'gcc'
   repeated string gcc_plugin_compiler_flag = 34;