clang/win: Take another stab at building with -Wunused-private-field.

third_party/libphonenumber/BUILD.gn

 # 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.
 
 import("//testing/test.gni")
 import("//third_party/protobuf/proto_library.gni")
 
 proto_library("proto") {
   sources = [
     "src/resources/phonemetadata.proto",
@@ skipping 33 matching lines @@
     "src/phonenumbers/utf/unicodetext.cc",
     "src/phonenumbers/utf/unilib.cc",
   ]
 
   # libphonenumber's base/logging.h is a minimal implementation where DCHECKs
   # do not consume their arguments. This leads to unused variable warnings in
   # release builds.
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
 
+  config("libphonenumber_without_metadata_warnings") {
+    if (is_clang) {
+      cflags = [
+        # https://github.com/googlei18n/libphonenumber/pull/741
+        "-Wno-unused-private-field",
+      ]
+    }
+  }
+  configs += [ ":libphonenumber_without_metadata_warnings" ]
+
   public_configs = [ ":libphonenumber_config" ]
 
   public_deps = [
     ":proto",
   ]
   deps = [
     ":proto",
     "//third_party/icu",
     "//third_party/protobuf:protobuf_lite",
   ]
@@ skipping 33 matching lines @@
   deps = [
     ":libphonenumber_without_metadata",
     "//base",
     "//base/test:run_all_unittests",
     "//base/third_party/dynamic_annotations",
     "//third_party/icu",
     "//testing/gmock",
     "//testing/gtest",
   ]
 }