Very common, cuts about 70k from pkg/tools/linux_amd64/* binaries.

Change-Id: Ied0c049e56e56a56810c781435d79027fbcaf274
Reviewed-on: https://go-review.googlesource.com/21374Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>