cmd/dist, cmd/go: make GODEBUG=godebughash=1 ./make.bash work better

cmd/dist, cmd/go: make GODEBUG=godebughash=1 ./make.bash work better

The change in cmd/dist ignores debug output, instead of assuming
any output is from the template.

The change in cmd/go makes the debug output show the package name
on every line, so that interlaced prints can be deinterlaced.

Change-Id: Ic3d59ee0256271067cb9be2fde643a0e19405375
Reviewed-on: https://go-review.googlesource.com/76019
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>