Remove Chromium Clang warnings only on Windows.

webrtc/system_wrappers/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.
 
 if (is_android) {
   import("//build/config/android/config.gni")
@@ skipping 115 matching lines @@
 
   # TODO(jschuh): Bug 1348: fix this warning.
   configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
 
   if (is_win) {
     libs += [ "winmm.lib" ]
 
     cflags = [ "/wd4334" ]  # Ignore warning on shift operator promotion.
   }
 
-  if (is_clang) {
+  if (is_win && is_clang) {
     # Suppress warnings from the Chromium Clang plugin (bugs.webrtc.org/163).
     configs -= [ "//build/config/clang:find_bad_constructs" ]
   }
 
   deps += [ "../base:rtc_base_approved" ]
 }
 
 source_set("field_trial_default") {
   sources = [
     "include/field_trial_default.h",
@@ skipping 96 matching lines @@
       "//testing/gtest",
     ]
 
     if (is_android) {
       deps += [ "//testing/android/native_test:native_test_support" ]
 
       shard_timeout = 900
     }
   }
 }