Enable the -Wundef warning for clang

webrtc/common_audio/signal_processing/signal_processing_unittest.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 <algorithm>
 #include <sstream>
 
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gtest.h"
 #include "webrtc/common_audio/signal_processing/include/signal_processing_library.h"
 
 static const size_t kVector16Size = 9;
 static const int16_t vector16[kVector16Size] = {1, -15511, 4323, 1963,
   WEBRTC_SPL_WORD16_MAX, 0, WEBRTC_SPL_WORD16_MIN + 5, -3333, 345};
 
 class SplTest : public testing::Test {
  protected:
    SplTest() {
      WebRtcSpl_Init();
@@ skipping 573 matching lines @@
   // 12-15 are skipped to account for the filter lag.
   for (size_t i = 0; i < 12; ++i) {
     EXPECT_EQ(kRefValue32kHz1, out_vector[i]);
     EXPECT_EQ(kRefValue16kHz1, out_vector_w16[i]);
   }
   for (size_t i = 16; i < 2 * kBlockSize; ++i) {
     EXPECT_EQ(kRefValue32kHz2, out_vector[i]);
     EXPECT_EQ(kRefValue16kHz2, out_vector_w16[i]);
   }
 }