MB: Don't treat warnings as errors for GCC.
MB: Don't treat warnings as errors for GCC.

This makes it possible to enable GCC compilation in our
main waterfall.

BUG=webrtc:7853
NOTRY=True

Change-Id: I99075c6f582e9b471eb7a4a2ea709bac67ceba86
Reviewed-on: https://chromium-review.googlesource.com/544998
Reviewed-by: Edward Lemur <d05609f027dc667cc37492b1dc1bdea5d60fa82a@webrtc.org>
Commit-Queue: Henrik Kjellander <60c11d3e646624f25a02b88f51d51ca6b7ff7c72@webrtc.org>
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#18721}
ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,TimothyGu/libilbc