pull gflags.gyp changes from webrtc

third_party/gflags/BUILD.gn

 #
 # Copyright 2014 The LibYuv 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.
 
 # This is a copy of WebRTC's BUILD.gn.
 
 if (is_win) {
   gflags_gen_arch_root = "gen/win"
 } else {
   gflags_gen_arch_root = "gen/posix"
 }
 
 config("gflags_config") {
- include_dirs = [
+  include_dirs = [
     "$gflags_gen_arch_root/include",  # For configured files.
     "src",  # For everything else.
   ]
 
   defines = [
     # These macros exist so flags and symbols are properly exported when
     # building DLLs. Since we don't build DLLs, we need to disable them.
     "GFLAGS_DLL_DECL=",
     "GFLAGS_DLL_DECLARE_FLAG=",
     "GFLAGS_DLL_DEFINE_FLAG=",
   ]
+
+  # GN orders flags on a target before flags from configs. The default config
+  # adds -Wall, and this flag have to be after -Wall -- so they need to
+  # come from a config and can't be on the target directly.
+  if (is_clang) {
+    cflags = [ "-Wno-unused-local-typedef" ]
+  }
 }
 
 source_set("gflags") {
   sources = [
     "src/gflags.cc",
     "src/gflags_completions.cc",
     "src/gflags_reporting.cc",
   ]
   if (is_win) {
     sources += [ "src/windows/port.cc" ]
 
     cflags = [
       "/wd4005",  # WIN32_LEAN_AND_MEAN.
       "/wd4267",  # Conversion from size_t to "type".
     ]
   }
 
-  include_dirs = [
-    "$gflags_gen_arch_root/include/private",  # For config.h
-  ]
+  include_dirs = [ "$gflags_gen_arch_root/include/private" ]  # For config.h
 
   public_configs = [ ":gflags_config" ]
 
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
 
   if (is_clang) {
     # TODO(andrew): Look into fixing this warning upstream:
     # http://code.google.com/p/webrtc/issues/detail?id=760
     configs -= [ "//build/config/clang:extra_warnings" ]
   }
 }
+