Enable the -Wundef warning for clang

webrtc/common_audio/ring_buffer_unittest.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/common_audio/ring_buffer.h"
 
 #include <stdlib.h>
 #include <time.h>
 
 #include <algorithm>
 #include <memory>
 
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gtest.h"
 
 namespace webrtc {
 
 struct FreeBufferDeleter {
   inline void operator()(void* ptr) const {
     WebRtc_FreeBuffer(ptr);
   }
 };
 typedef std::unique_ptr<RingBuffer, FreeBufferDeleter> scoped_ring_buffer;
 
@@ skipping 111 matching lines @@
 
 TEST(RingBufferTest, CreateHandlesErrors) {
   EXPECT_TRUE(WebRtc_CreateBuffer(0, 1) == NULL);
   EXPECT_TRUE(WebRtc_CreateBuffer(1, 0) == NULL);
   RingBuffer* buffer = WebRtc_CreateBuffer(1, 1);
   EXPECT_TRUE(buffer != NULL);
   WebRtc_FreeBuffer(buffer);
 }
 
 }  // namespace webrtc