cmd/go: add TestACL

Add test that verifies that go command produces executable
that have security attributes of the target directory.

Update #22343

Change-Id: Ieab02381927a2b09bee21c49c043b3298bd088e6
Reviewed-on: https://go-review.googlesource.com/78215


Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>