Add test, and while we're at here, also add a test for ARM.

Fixes #10343.

Change-Id: Ic914df8233d4f1f495e2cc0743fbd37b7671bc91
Signed-off-by: Shenghou Ma <minux@golang.org>
Reviewed-on: https://go-review.googlesource.com/8472Reviewed-by: Aram Hăvărneanu <aram@mgk.ro>
Reviewed-by: Rob Pike <r@golang.org>