cmd/compilebench: add -pkg flag to compile a single package

Sometimes, as with CL 41493, or when investigating
a reported issue, there's a package of interest
that is not part of the standard compilebench suite.
Add a -pkg flag to allow easy access to the compilebench
set of goodies (allocs, object file stats) without
having to edit and reinstall compilebench itself,
which is what I have been doing.

Change-Id: Id6ca6356cae062208f8686c0cb597ed45fc861c0
Reviewed-on: https://go-review.googlesource.com/41627
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
1 file changed