Remove ".." from include_dirs in build/common.

BUG=1662
TEST=compile on trybots
R=tina.legrand@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/2332004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@5107 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/modules/audio_coding/codecs/opus/opus.gypi b/webrtc/modules/audio_coding/codecs/opus/opus.gypi
index b60cee5..4068702 100644
--- a/webrtc/modules/audio_coding/codecs/opus/opus.gypi
+++ b/webrtc/modules/audio_coding/codecs/opus/opus.gypi
@@ -23,6 +23,9 @@
           ],
         }],
       ],
+      'include_dirs': [
+        '<(webrtc_root)',
+      ],
       'sources': [
         'interface/opus_interface.h',
         'opus_interface.c',