Refactor matrix script

[ntkme]

@eregon Please take a look if this looks good to you.

[eregon]

Thank you!
I totally missed that variable 😅

[eregon]

BTW do you have an idea how to apply this to all truffleruby/truffleruby+graalvm versions >= 34 (so head, 34, 40, etc), although 34, 40 are not out yet, but it'd be nice if CI doesn't break when they are.

[eregon]

Ah given truffleruby_versions = %w[truffleruby truffleruby-head truffleruby+graalvm truffleruby+graalvm-head] it's actually trivial, we just need to wait for 34 to be out then, and it'll be fixed for versions after that.

(sorry, it's late here)

[ntkme]

In theory, it can be done by checking the latest version available in ruby-builder-versions.json, and generating the matrix differently. However, I think trying to handle a future change before it comes out seems to be a bit over-engineered for a simple one-time issue.

---

As 34 come out, as part of the ruby-builder-bot PR, we can just manually add a commit to have it changed from:

truffleruby_versions = %w[truffleruby truffleruby-head truffleruby+graalvm truffleruby+graalvm-head]
matrix += non_windows_runners.product(truffleruby_versions)

To:

truffleruby_versions = %w[truffleruby truffleruby-head truffleruby+graalvm truffleruby+graalvm-head]
matrix += (macos_arm64_runners + ubuntu_runners).product(truffleruby_versions)