[Mac/GN] Add missing -Wobjc-missing-property-synthesis.

build/config/mac/BUILD.gn

 # Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/sysroot.gni")
 import("//build/config/mac/mac_sdk.gni")
 import("//build/config/mac/symbols.gni")
 
 # This is included by reference in the //build/config/compiler config that
 # is applied to all targets. It is here to separate out the logic.
@@ skipping 46 matching lines @@
 config("runtime_library") {
   common_flags = [
     "-isysroot",
     sysroot,
     "-mmacosx-version-min=$mac_deployment_target",
   ]
 
   asmflags = common_flags
   cflags = common_flags
   ldflags = common_flags
+
+  if (is_mac) {
+    # Prevent Mac OS X AssertMacros.h from defining macros that collide
+    # with common names, like 'check', 'require', and 'verify'.
+    # (Included by system header. Also exists on iOS but not included.)
+    # http://opensource.apple.com/source/CarbonHeaders/CarbonHeaders-18.1/AssertMacros.h
+    defines = [ "__ASSERT_MACROS_DEFINE_VERSIONS_WITHOUT_UNDERSCORE=0" ]
+  }
 }
 
 # On Mac, this is used for everything except static libraries.
 config("mac_dynamic_flags") {
   ldflags = []
 
   if (is_component_build) {
     ldflags += [
       # Path for loading shared libraries for unbundled binaries.
       "-Wl,-rpath,@loader_path/.",
@@ skipping 15 matching lines @@
 # //build/toolchain/mac/linker_driver.py.
 # Remove this config if a target wishes to change the arguments passed to the
 # strip command during linking. This config by default strips all symbols
 # from a binary, but some targets may wish to specify a saves file to preserve
 # specific symbols.
 config("strip_all") {
   if (enable_stripping) {
     ldflags = [ "-Wcrl,strip,-x,-S" ]
   }
 }