Right now, if clang-format is broken, a CL will still pass CQ.
This adds a flag so that it will fail CQ.

Bug: 911708
Change-Id: I2c71b7bc434fc611d51f688266be6a265b80f4da
Reviewed-on: https://chromium-review.googlesource.com/c/1361560Reviewed-by: agrieve <agrieve@chromium.org>
Commit-Queue: Ryan Tseng <hinoka@chromium.org>