Enable the -Wundef warning for clang

webrtc/modules/audio_device/test/audio_device_test_api.cc

 /*
  *  Copyright (c) 2012 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 <math.h>
 #include <stdio.h>
 #include <string.h>
 
 #include <memory>
 
 #include "webrtc/modules/audio_device/test/audio_device_test_defines.h"
 
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gtest.h"
 #include "webrtc/test/testsupport/fileutils.h"
 
 #include "webrtc/modules/audio_device/audio_device_config.h"
 #include "webrtc/modules/audio_device/audio_device_impl.h"
 #include "webrtc/system_wrappers/include/sleep.h"
 
 // Helper functions
 #if defined(ANDROID)
 char filenameStr[2][256] =
 { {0},
@@ skipping 1781 matching lines @@
   // TODO(kjellander): Fix so these tests pass on Mac.
 #if !defined(WEBRTC_MAC)
   EXPECT_EQ(0, audio_device_->InitPlayout());
   EXPECT_EQ(0, audio_device_->StartPlayout());
 #endif
 
   EXPECT_EQ(-1, audio_device_->GetLoudspeakerStatus(&loudspeakerOn));
 #endif
   EXPECT_EQ(0, audio_device_->StopPlayout());
 }