We were not being consistent.
Standardize on toolchain.

Change-Id: Id0e756b5214ce4a1341f733634ed95263f03a61c
Reviewed-on: https://go-review.googlesource.com/87017
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>