* automate setup-go-work
It's all to easy to forget to `make setup-go-work`, only to run into mysterious build failures. Let's default to doing this automatically, unless `SKIP_SETUP_GO_WORK` is true (or the legacy `IGNORE_GO_WORK_IF_EXISTS`, which was oddly named, since we can't actually ignore it.)
* Make setup-go-work recipe fail-fast with set -e