Add presubmit check for .gclient file Bug: angleproject:4905 Change-Id: I6dbb81ed2d2e102869e5d844fed1bb4c1ef4f449 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3720557 Reviewed-by: Cody Northrop <cnorthrop@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Eddie Hatfield <eddiehatfield@google.com>