cmd/go: add a missing curly-brace in the 'stale' command format string
The missing brace made the 'stale' command a no-op in the non-error case.
Fix the 'short' skip in install_cross_gobin (it was backward) and
update it to no longer check staleness of a not-necessarily-stale
target and to no longer expect to be able to install into GOROOT/pkg.
(This was missed in #30316 because that part of the test was
erroneously skipped in non-short mode.)
Change-Id: I6a276fec5fa5e5da3fe0daf0c2b5086116ed7c1a
Reviewed-on: https://go-review.googlesource.com/c/go/+/223747
Run-TryBot: Bryan C. Mills <bcmills@google.com> Reviewed-by: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>