Extract common build steps to composite actions

[mgeisler]

This allows us to repeat ourselves less across the different jobs.

I also tested using a “reusable workflow” to factor out the common steps. However, this starts a separate job without a shared file system, which in turn requires us to upload/download artifacts when we want to use them in several jobs. The artifacts are downloaded one-by-one and this adds delays and extra steps to all jobs.