Ensure GHA jobs fail fast in scripts

[jakebailey]

GitHub Actions has a surprising default; scripts do not get pipefile and don't fail-fast when one command fails.

The documented workaround is to set the default to bash, which enables this behavior. See: https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#exit-codes-and-error-action-preference