Modify the gcc_toolchain definitions in GN for NaCl compatibility

build/config/BUILDCONFIG.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.
 
 # =============================================================================
 # PLATFORM SELECTION
 # =============================================================================
 #
 # There are two main things to set: "os" and "cpu". The "toolchain" is the name
 # of the GN thing that encodes combinations of these things.
@@ skipping 397 matching lines @@
 if (is_linux) {
   _native_compiler_configs += [ "//build/config/linux:sdk" ]
 } else if (is_mac) {
   _native_compiler_configs += [ "//build/config/mac:sdk" ]
 } else if (is_ios) {
   _native_compiler_configs += [ "//build/config/ios:sdk" ]
 } else if (is_android) {
   _native_compiler_configs += [ "//build/config/android:sdk" ]
 }
 
-if (is_clang) {
+if (is_clang && !is_nacl) {
   _native_compiler_configs += [
     "//build/config/clang:find_bad_constructs",
     "//build/config/clang:extra_warnings",
   ]
 }
 
 # Optimizations and debug checking.
 if (is_debug) {
   _native_compiler_configs += [ "//build/config:debug" ]
   _default_optimization_config = "//build/config/compiler:no_optimize"
@@ skipping 189 matching lines @@
     forward_variables_from(invoker, "*")
 
     # All shared libraries must have the sanitizer deps to properly link in
     # asan mode (this target will be empty in other cases).
     if (!defined(deps)) {
       deps = []
     }
     deps += [ "//build/config/sanitizers:deps" ]
   }
 }