Make angle's commit.h depend on git head This is for reproducible build of angle related libraries. Bug: 828669 Change-Id: I807c8fb01b976f6e7a71477ee934b9e0b0cdc684 Reviewed-on: https://chromium-review.googlesource.com/1164814 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Frank Henigman <fjhenigman@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>