Make our CI feedback loop shorter

This is about the follow-up work to #15501 (closed) that we want to do in 2019-2020, i.e.:

1. Get in touch with ProfitBricks, that donate crazy amounts of VM “hardware” to the Reproducible Builds project. If they’re happy to give us some, this would be, by far, the simplest and cheapest option. AFAIK that’s a simple “here’s a VM, you’re root” setup so it does not have the drawbacks of more powerful & complex cloud systems, apart of course the fact we don’t run the hardware ourselves.
2. Decide between ProfitBricks and the “hacker option”.
3. Implement the chosen solution.

Blueprint: https://tails.boum.org/blueprint/hardware_for_automated_tests_take3/

Related issues

• Related to #11680 (closed)
• Related to #17216
• Blocks #13284
• Follows #15501 (closed)

Original created by @intrigeri on 16960 (Redmine)