Enable the -Wundef warning for clang

webrtc/modules/audio_processing/transient/transient_suppression_test.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 "webrtc/modules/audio_processing/transient/transient_suppressor.h"
 
 #include <stdlib.h>
 #include <stdio.h>
 
 #include <memory>
 #include <string>
 
 #include "gflags/gflags.h"
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gtest.h"
 #include "webrtc/common_audio/include/audio_util.h"
 #include "webrtc/modules/audio_processing/agc/agc.h"
 #include "webrtc/modules/include/module_common_types.h"
 #include "webrtc/test/testsupport/fileutils.h"
 #include "webrtc/typedefs.h"
 
 DEFINE_string(in_file_name, "", "PCM file that contains the signal.");
 DEFINE_string(detection_file_name,
               "",
               "PCM file that contains the detection signal.");
@@ skipping 211 matching lines @@
 }
 
 }  // namespace webrtc
 
 int main(int argc, char* argv[]) {
   google::SetUsageMessage(webrtc::kUsage);
   google::ParseCommandLineFlags(&argc, &argv, true);
   webrtc::void_main();
   return 0;
 }