This will do a go list using a filename directly if listing using
the directory failed.
Fixesgolang/go#32587
Change-Id: Id9993968f0ebc18a455132e0f1468356416a66dd
Reviewed-on: https://go-review.googlesource.com/c/tools/+/182465
Run-TryBot: Michael Matloob <matloob@golang.org>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>