Enable the -Wundef warning for clang

webrtc/modules/audio_processing/test/unpack.cc

Index: webrtc/modules/audio_processing/test/unpack.cc
diff --git a/webrtc/modules/audio_processing/test/unpack.cc b/webrtc/modules/audio_processing/test/unpack.cc
index d3f163383246fb3b7dad913f7e9c780960496309..61e1ebe91c233e10290d7b46841981ae12ac1fa7 100644
--- a/webrtc/modules/audio_processing/test/unpack.cc
+++ b/webrtc/modules/audio_processing/test/unpack.cc
@@ -19,11 +19,15 @@
 
 #include "gflags/gflags.h"
 #include "webrtc/base/format_macros.h"
-#include "webrtc/modules/audio_processing/debug.pb.h"
+#include "webrtc/base/ignore_wundef.h"
 #include "webrtc/modules/audio_processing/test/protobuf_utils.h"
 #include "webrtc/modules/audio_processing/test/test_utils.h"
 #include "webrtc/typedefs.h"
 
+RTC_PUSH_IGNORING_WUNDEF()
+#include "webrtc/modules/audio_processing/debug.pb.h"
+RTC_POP_IGNORING_WUNDEF()
+
 // TODO(andrew): unpack more of the data.
 DEFINE_string(input_file, "input", "The name of the input stream file.");
 DEFINE_string(output_file, "ref_out",