Add arc-host-clock

BUG=b:166087457
TEST=build

Change-Id: I610be9e33bf4f368bf11f09012e95eef9d150f5b
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/eclass-overlay/+/2376942
Tested-by: Ryo Hashimoto <hashimoto@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Ryo Hashimoto <hashimoto@chromium.org>