Location lists are only supported on x86 and amd64, so the
test expecting them failed everywhere else. Make that test
skip unless GOARCH is x86 or amd64.

Change-Id: Id86b34d30c6a0b97e6fa0cd5aca31f51ed84f556
Reviewed-on: https://go-review.googlesource.com/84395
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>