Only disable -Wthread-safety-attributes warning for Clang.

webrtc/modules/video_coding/BUILD.gn

 # Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 import("../../webrtc.gni")
 
@@ skipping 130 matching lines @@
     "../../rtc_base:rtc_base_approved",
     "../../rtc_base:rtc_numerics",
     "../../rtc_base:rtc_task_queue",
     "../../rtc_base:sequenced_task_checker",
     "../../system_wrappers",
   ]
 }
 
 # TODO(ehmaldonado): Remove once http://bugs.webrtc.org/8090 is fixed.
 config("webrtc_h264_config") {
-  cflags = [ "-Wno-thread-safety-attributes" ]
+  if (is_clang) {
+    cflags = [ "-Wno-thread-safety-attributes" ]
+  }
 }
 
 rtc_static_library("webrtc_h264") {
   sources = [
     "codecs/h264/h264.cc",
     "codecs/h264/include/h264.h",
   ]
 
   if (!build_with_chromium && is_clang) {
     # Suppress warnings from the Chromium Clang plugin (bugs.webrtc.org/163).
@@ skipping 479 matching lines @@
     }
 
     # TODO(jschuh): bugs.webrtc.org/1348: fix this warning.
     configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
     if (!build_with_chromium && is_clang) {
       # Suppress warnings from the Chromium Clang plugin (bugs.webrtc.org/163).
       suppressed_configs += [ "//build/config/clang:find_bad_constructs" ]
     }
   }
 }