Build both standalone and Chromium gTest targets. This will let us pick the standalone test version when trying out the new test runner. GN-only change. Bug: angleproject:3162 Change-Id: I08c75c7a38aaf63c5a25cc8623eb05615cc29abb Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2229068 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Jonah Ryan-Davis <jonahr@google.com>