Some arm-specific files were not part of the build.

BUG=angleproject:4026

Change-Id: Ie3534c66ebce53348a00f74b95b7f6e3859ee30f
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1866079Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Geoff Lang <geofflang@chromium.org>