Enable the -Wundef warning for clang

webrtc/base/logging.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.
  */
 
@@ skipping 317 matching lines @@
 #define LOG_GLE(sev) \
   LOG_GLE_EX(sev, GetLastError())
 #define LOG_GLEM(sev, mod) \
   LOG_E(sev, HRESULT, GetLastError(), mod)
 #define LOG_ERR_EX(sev, err) \
   LOG_GLE_EX(sev, err)
 #define LOG_ERR(sev) \
   LOG_GLE(sev)
 #define LAST_SYSTEM_ERROR \
   (::GetLastError())
-#elif __native_client__
+#elif defined(__native_client__) && __native_client__
 #define LOG_ERR_EX(sev, err) \
   LOG(sev)
 #define LOG_ERR(sev) \
   LOG(sev)
 #define LAST_SYSTEM_ERROR \
   (0)
 #elif defined(WEBRTC_POSIX)
 #define LOG_ERR_EX(sev, err) \
   LOG_ERRNO_EX(sev, err)
 #define LOG_ERR(sev) \
   LOG_ERRNO(sev)
 #define LAST_SYSTEM_ERROR \
   (errno)
 #endif  // WEBRTC_WIN
 
 #define LOG_TAG(sev, tag) \
   LOG_SEVERITY_PRECONDITION(sev) \
     rtc::LogMessage(NULL, 0, sev, tag).stream()
 
 #define PLOG(sev, err) \
   LOG_ERR_EX(sev, err)
 
 // TODO(?): Add an "assert" wrapper that logs in the same manner.
 
 #endif  // LOG
 
 }  // namespace rtc
 
 #endif  // WEBRTC_BASE_LOGGING_H_