test `donate-cpu.py` in the CI
This is a "blackbox test" to ensure it works. We also need more unit tests.
Unfortunately this would initiate builds of the latest source and a previous version but we only want to test that the script is actually works in the first case.
Maybe we could add a test mode which passes a list of versions and the respective binary. That would allow us to leverage an existing binary and run at least some basic blackbox tests. We could integrate it into the scriptcheck and even do this across the various Python versions.
On a side note - I always wanted the amount of versions to be actually dynamic so we could be able to compare more than two versions. Comparing it with the last two stable releases would greatly help with identify some regressions even after a new release.