Enable the -Wundef warning for clang

webrtc/common_audio/audio_util_unittest.cc

 /*
  *  Copyright (c) 2013 The WebRTC 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.
  */
 
-#include "testing/gmock/include/gmock/gmock.h"
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gmock.h"
+#include "webrtc/test/gtest.h"
 #include "webrtc/common_audio/include/audio_util.h"
 #include "webrtc/typedefs.h"
 
 namespace webrtc {
 namespace {
 
 using ::testing::ElementsAreArray;
 
 void ExpectArraysEq(const int16_t* ref, const int16_t* test, size_t length) {
   for (size_t i = 0; i < length; ++i) {
@@ skipping 199 matching lines @@
     const int16_t expected[kNumFrames] = {28000, -11, -30333};
 
     DownmixToMono<int16_t, int32_t>(input, kNumFrames, kNumChannels, downmixed);
 
     EXPECT_THAT(downmixed, ElementsAreArray(expected));
   }
 }
 
 }  // namespace
 }  // namespace webrtc