This retires the ANGLE BUILD.gn file for glslang. Also makes a few more
repos sync from Chromium's copy using build overrides. This should
speed up Chrome checkouts slightly.

Bug: angleproject:3088
Change-Id: I530f28d9b13469bbe6471a4c61e7353d599d81ec
Reviewed-on: https://chromium-review.googlesource.com/c/1422545Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Tobin Ehlis <tobine@google.com>
Commit-Queue: Jamie Madill <jmadill@chromium.org>