Previously help for flags was printed to stderr.
This CL makes all the output to be printed to stdout.
Updates golang/go#31885
Change-Id: If95edeccd79581326502dd5c7fc2b49d8f160be7
Reviewed-on: https://go-review.googlesource.com/c/tools/+/175900
Reviewed-by: Ian Cottrell <iancottrell@google.com>
Run-TryBot: Ian Cottrell <iancottrell@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>