gotest: fix handling of --goarch option

I managed to add a new --goarch option to gotest without noticing that
the script already had one.  Worse, they set different variables.
Remove the old option in favor of the new one.

Change-Id: I6d37eea7dc13ceac9475fe6d557532477c315507
Reviewed-on: https://go-review.googlesource.com/16613
Reviewed-by: Ian Lance Taylor <iant@golang.org>
3 files changed