Enable the -Wundef warning for clang

webrtc/base/sequenced_task_checker_unittest.cc

Index: webrtc/base/sequenced_task_checker_unittest.cc
diff --git a/webrtc/base/sequenced_task_checker_unittest.cc b/webrtc/base/sequenced_task_checker_unittest.cc
index 2450bd5175061c39eacbf3e635be37170bedaa2a..13b1afc50a9e64ec52c9f0248ea30bf8c516f66c 100644
--- a/webrtc/base/sequenced_task_checker_unittest.cc
+++ b/webrtc/base/sequenced_task_checker_unittest.cc
@@ -7,7 +7,7 @@
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gtest.h"
 #include "webrtc/base/checks.h"
 #include "webrtc/base/constructormagic.h"
 #include "webrtc/base/platform_thread.h"
@@ -197,7 +197,7 @@ TEST(SequencedTaskCheckerTest, DetachFromTaskQueueAndUseOnThread) {
   EXPECT_TRUE(done_event.Wait(1000));
 }
 
-#if !NDEBUG || DCHECK_ALWAYS_ON
+#if !defined(NDEBUG) || DCHECK_ALWAYS_ON
 TEST(SequencedTaskCheckerTest, MethodNotAllowedOnDifferentThreadInDebug) {
   RunMethodOnDifferentThread(false);
 }
@@ -207,7 +207,7 @@ TEST(SequencedTaskCheckerTest, MethodAllowedOnDifferentThreadInRelease) {
 }
 #endif
 
-#if !NDEBUG || DCHECK_ALWAYS_ON
+#if !defined(NDEBUG) || DCHECK_ALWAYS_ON
 TEST(SequencedTaskCheckerTest, MethodNotAllowedOnDifferentTaskQueueInDebug) {
   RunMethodOnDifferentTaskQueue(false);
 }
@@ -217,7 +217,7 @@ TEST(SequencedTaskCheckerTest, MethodAllowedOnDifferentTaskQueueInRelease) {
 }
 #endif
 
-#if !NDEBUG || DCHECK_ALWAYS_ON
+#if !defined(NDEBUG) || DCHECK_ALWAYS_ON
 TEST(SequencedTaskCheckerTest, DetachFromTaskQueueInDebug) {
   DetachThenCallFromDifferentTaskQueue(false);
 }