PRESUBMIT: Exclude overrides paths from source above GYP check.
PRESUBMIT: Exclude overrides paths from source above GYP check.

Since base.gyp contains a couple of those.

BUG=4185
TESTED=Ran git cl presubmit with a modified base.gyp without this patch - got errors about overrides. Ran another time with this patch applied - no errors.
TBR=pthatcher@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/44529004

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#8586}
git-svn-id: 917f5d3ca488f358c4d40eaec14422cf392ccec9@8586 4adac7df-926f-26a2-2b94-8c16560cd09d

TimothyGu/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc