Build platforms

[maxb2]

Continuing the discussion from leafac/caxa#30.

• Github Actions is 6 hours per job.
• Azure Pipelines is 6 hours per job.
• Travis CI is 50 minutes per job
• Gitlab is 3 hours per project on shared runners. Gitlab offers 50k CI minutes monthly for qualifying open source projects.
• CircleCI is 5 hours per job. CircleCI offers 400k credits monthly for qualifying open source projects.

Gitlab and CircleCI might work if there are no individual job timeouts (I can't find it anywhere), but you have to apply for those programs. I may try them in the future when I have time to apply and learn a new CI system.

Breaking the compilation into chunks may be the only option without costing money. Might as well keep it on Github then.

I don't believe there are any good options without setting up our own hardware to run these jobs. If anyone finds other options, please share!