Enable the -Wundef warning for clang

webrtc/modules/audio_processing/beamformer/array_util_unittest.cc

 /*
  *  Copyright (c) 2015 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.
  */
 
 // MSVC++ requires this to be set before any other includes to get M_PI.
 #define _USE_MATH_DEFINES
 
 #include "webrtc/modules/audio_processing/beamformer/array_util.h"
 
 #include <math.h>
 #include <vector>
 
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gtest.h"
 
 namespace webrtc {
 
 bool operator==(const Point& lhs, const Point& rhs) {
   return lhs.x() == rhs.x() && lhs.y() == rhs.y() && lhs.z() == rhs.z();
 }
 
 TEST(ArrayUtilTest, PairDirection) {
   EXPECT_EQ(Point(1.f, 2.f, 3.f),
             PairDirection(Point(0.f, 0.f, 0.f), Point(1.f, 2.f, 3.f)));
@@ skipping 146 matching lines @@
   EXPECT_FLOAT_EQ(-45.f, RadiansToDegrees(-M_PI / 4.f));
   EXPECT_FLOAT_EQ(60.f, RadiansToDegrees(M_PI / 3.f));
   EXPECT_FLOAT_EQ(-90.f, RadiansToDegrees(-M_PI / 2.f));
   EXPECT_FLOAT_EQ(120.f, RadiansToDegrees(2.f * M_PI / 3.f));
   EXPECT_FLOAT_EQ(-135.f, RadiansToDegrees(-3.f * M_PI / 4.f));
   EXPECT_FLOAT_EQ(150.f, RadiansToDegrees(5.f * M_PI / 6.f));
   EXPECT_FLOAT_EQ(-180.f, RadiansToDegrees(-M_PI));
 }
 
 }  // namespace webrtc