Enable the -Wundef warning for clang

webrtc/modules/audio_coding/neteq/audio_classifier_unittest.cc

 /*
  *  Copyright (c) 2014 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_coding/neteq/audio_classifier.h"
 
 #include <math.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <memory>
 #include <string>
 
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gtest.h"
 #include "webrtc/test/testsupport/fileutils.h"
 
 namespace webrtc {
 
 static const size_t kFrameSize = 960;
 
 TEST(AudioClassifierTest, AllZeroInput) {
   int16_t in_mono[kFrameSize] = {0};
 
   // Test all-zero vectors and let the classifier converge from its default
@@ skipping 42 matching lines @@
 #endif // WEBRTC_ARCH_ARM
 }
 
 TEST(AudioClassifierTest, DoAnalysisStereo) {
   RunAnalysisTest(test::ResourcePath("short_mixed_stereo_48", "pcm"),
                   test::ResourcePath("short_mixed_stereo_48", "dat"),
                   2);
 }
 
 }  // namespace webrtc