Broken CI build

[flavorjones]

The build is broken, and I think there are a couple of unrelated reasons why.

1. linux builds are broken during the gem test because of the problem I'm trying to address upstream in rake-compiler
   • example https://github.com/rake-compiler/rake-compiler-dock/actions/runs/3696448796/jobs/6260158246#step:7:125
   • upstream fix: https://github.com/rake-compiler/rake-compiler/pull/209 (please review!)
   • workaround: #81
2. other builds are broken while building the docker images, need to dig in on this.
   • example: https://github.com/rake-compiler/rake-compiler-dock/actions/runs/3696448796/jobs/6260158392#step:5:1068

We should also set up periodic builds to make sure bitrot isn't setting in over time. This would have been great to catch earlier.

@larskanis can you take a look at the rake-compiler PR when you have a moment, that feels like a blocker.