Enable the -Wundef warning for clang

webrtc/base/gunit.h

 /*
  *  Copyright 2004 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.
  */
 
 #ifndef WEBRTC_BASE_GUNIT_H_
 #define WEBRTC_BASE_GUNIT_H_
 
 #include "webrtc/base/fakeclock.h"
 #include "webrtc/base/logging.h"
 #include "webrtc/base/thread.h"
 #if defined(GTEST_RELATIVE_PATH)
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gtest.h"
 #else
 #include "testing/base/public/gunit.h"
 #endif
 
 // Wait until "ex" is true, or "timeout" expires.
 #define WAIT(ex, timeout)                                       \
   for (int64_t start = rtc::SystemTimeMillis();                 \
        !(ex) && rtc::SystemTimeMillis() < start + (timeout);) { \
     rtc::Thread::Current()->ProcessMessages(0);                 \
     rtc::Thread::Current()->SleepMs(1);                         \
@@ skipping 111 matching lines @@
 
 #define ASSERT_EQ_SIMULATED_WAIT(v1, v2, timeout, clock) \
   do {                                                   \
     bool res;                                            \
     SIMULATED_WAIT_(v1 == v2, timeout, res, clock);      \
     if (!res)                                            \
       ASSERT_EQ(v1, v2);                                 \
   } while (0)
 
 #endif  // WEBRTC_BASE_GUNIT_H_