ci: Upgrade workflow versions

[liyishuai]

• opam install should show a hint when installing post dependencies ocaml/opam#6109

[pmetzger]

Seems sane to me. Do you know why the CI is spitting up on this change?

[liyishuai]

GitHub has upgraded the latest version of Mac to use ARM chips, which the old version of setup-ocaml doesn't like. The new version of setup-ocaml drops support for old versions of OCaml on some OS's. I'll try to figure out how to support the most OS*OCaml versions possible.

[pmetzger]

It would certainly be nice to have at least some x86 + Mac coverage.

[pmetzger]

BTW, if you want to look more broadly at the ocaml-community CI workflows, that would be very welcome.

[pmetzger]

@liyishuai let us know when you feel ready to commit this.

[liyishuai]

Almost there.

The current failure says uninstallation unsuccessful. Not sure why OPAM tries to install packages in an uninstall command.

[pmetzger]

@liyishuai BTW, you should now have direct commit access.

[pmetzger]

@liyishuai Feel free to commit when you feel it's appropriate.

[pmetzger]

@liyishuai If you had time to fix up the CI for the other stuff in ocaml-community it would be a real help!

[liyishuai]

I saw many other projects use https://github.com/ocurrent/ocaml-ci instad of GitHub Actions.

• For Cppo: I propose keeping the CI as-is, unless OCaml-CI has a better support for testing the dependants.
• For community projects with no CI yet: I'll open an issue that suggests choosing a platform, and offer help for GH Actions.
• For existing projects with GH Actions: I can start working on them, while keeping track of Documentation for compatibility ocaml/setup-ocaml#828. Expect low bandwidth as I'm caught in works recently.

[pmetzger]

Your plan seems fine! Thank you so much for your help!