cgo: fix _cgo_run timestamp file order
cgo: fix _cgo_run timestamp file order

The timestamp file is being created before cgo
runs, which means errors will not prevent it
from being created and thus will cause the
build to break by rendering the rule up-to-date
when it isn't.

R=rsc
CC=golang-dev
http://codereview.appspot.com/4001049

Committer: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go