Considering switching CI

[Arcterus]

I'm not really satisfied with Appveyor and Travis. The builds are pretty slow, so I'm considering switching to Circle CI or Azure Pipelines or something. There are a bunch of options in this discussion.

It might be best to just leave the macOS builds on Travis and switch Linux and Windows to something else, but I also don't really like having to maintain so many different types of CI.

Cirrus CI (which is what we now use for FreeBSD) support 8 Linux, 2 Windows, 2 FreeBSD, and 1 macOS build at the same time, so we could also just switch to that and call it a day. I feel like it will still be too slow though for the Windows and macOS builds at least.

[samuela]

Another option these days is GitHub Actions. Here's what I'm using for rustybox: https://github.com/samuela/rustybox/blob/master/.github/workflows/rust.yml.

[rivy]

Here's a GitHub Action workflow that I designed for lsd ...

• CICD.yml
• and the merged PR, for further explanation