Since the length of the hash is known prior to compilation, it can be
compared with script-generated hashes.

BUG=angleproject:2267
TEST=angle_unittests

Change-Id: Ia0a78dfd450c4ea2d526da7f3495b9750dcbd1af
Reviewed-on: https://chromium-review.googlesource.com/931884Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>