Fix imports in gcc_toolchain.gni to not rely on //tools.

build/config/android/config.gni

 # Copyright 2014 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.
 
 # This file contains common system config stuff for the Android build.
 
 if (is_android) {
   assert(rebase_path("//", root_build_dir) == "../../",
          "Android output directory must be nested 2 levels within src/ (" +
              "e.g.: out-gn/Debug). http://crbug.com/412935")
@@ skipping 305 matching lines @@
   if (defined(android_secondary_abi_cpu)) {
     if (is_clang) {
       android_secondary_abi_toolchain =
           "//build/toolchain/android:clang_${android_secondary_abi_cpu}"
     } else {
       android_secondary_abi_toolchain =
           "//build/toolchain/android:${android_secondary_abi_cpu}"
     }
   }
 }
+
+declare_args() {
+  # Enables used resource whitelist generation. Set for official builds only
+  # as a large amount of build output is generated.
+  enable_resource_whitelist_generation = is_android && is_official_build
+}