The test case was importing golang.org/x/build/cmd/cl,
which is a package main and cannot be imported.
The test case (stored in a separate repo) has been changed
to import golang.org/x/build/gerrit. Update the test accordingly.

Fixes #17702.

Change-Id: I80e150092111b5a04bb00c992b32edb271edb086
Reviewed-on: https://go-review.googlesource.com/32616
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>