Run tests as part of nightly builds

[atomb]

We currently run tests on PR creation and merges to master, but not with the nightly builds. I'd feel more comfortable if the builds we were providing for download had been directly tested (even though the above tests should always cover the same code). This would also give us an option for adding some longer-running tests that won't hold up PRs.

[robdockins]

@atomb, is this still the case?

[atomb]

Looks like this is fixed, as evidenced in last night's build: https://github.com/GaloisInc/saw-script/actions/runs/982239117