Enable the -Wundef warning for clang

webrtc/modules/audio_coding/audio_network_adaptor/fec_controller_unittest.cc

 /*
  *  Copyright (c) 2016 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 <utility>
 
 #include "webrtc/modules/audio_coding/audio_network_adaptor/fec_controller.h"
 #include "webrtc/modules/audio_coding/audio_network_adaptor/mock/mock_smoothing_filter.h"
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gtest.h"
 
 namespace webrtc {
 
 using ::testing::NiceMock;
 using ::testing::Return;
 using ::testing::_;
 
 namespace {
 
 // The test uses the following settings:
@@ skipping 277 matching lines @@
                         kEnablingBandwidthHigh, kEnablingPacketLossAtHighBw),
               Threshold(kDisablingBandwidthLow, kDisablingPacketLossAtLowBw,
                         kDisablingBandwidthHigh, kDisablingPacketLossAtHighBw),
               0, nullptr),
           std::move(mock_smoothing_filter))),
       "Check failed");
 }
 #endif
 
 }  // namespace webrtc