cmd/go: don't print cached output for non-build list commands

cmd/go: don't print cached output for non-build list commands

If a user is running a go list command that wouldn't trigger a build
(for example if -export was passed), don't print the cached stdout
outputs for previous builds of the artifacts.

Fixes #56375

Change-Id: I1d3e6c01d0eb3dada941bb2783ce2ac69aa3d5d2
Reviewed-on: https://go-review.googlesource.com/c/go/+/444836
Run-TryBot: Michael Matloob <matloob@golang.org>
Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Michael Matloob <matloob@golang.org>