Support clangarm64 compiler downgrade in the future

[ntkme]

See discussion in #21

[ntkme]

@MSP-Greg This PR adds code needed if we every need to downgrade clangarm64 in the future. If that really happens, you will have to upload all the packages in the list and then just change the version number.

[MSP-Greg]

@ntkme

Thanks. You've seen the gcc commit, which was due to Windows Ruby CI on GitHub Actions crashing and burning anywhere an extension gem was installed. There's a PR in Ruby master that fixes the gcc 15 issue, but older Ruby versions will have problems.

A long time ago, there were simply three packages, MSYS2, MINGW, & UCRT (maybe no UCRT, not sure). Then OpenSSL 3 was released, and there was a need for testing with it, so more packages were added, since older Rubies weren't compatible with it. Now, there's the issue with gcc.

So, I want to take a minute and think about the best way to organize the code so it allows for adding new packages, as gcc 15 packages should be added.

A long time ago this framework (setup-msys2-gcc, setup-ruby, setup-ruby-pkgs, and the various repos building all the pre-packaged Rubies) was put in place to do the following:

1. Allow 'non Windows' repo maintainers to add Windows jobs in a way that 'just works'.
2. Minimize caching in repos
3. Keep most of the traffic within the GitHub.com domain
4. Make it as fast as possible

I don't know if you recall the Travis/Appveyor days, but it was not fun.

Anyway, are you okay with me closing this?

Lastly, thanks for checking the code in your PR that added arm64 support. The CI is showing:
'** No update to clangarm64 gcc tools needed **', so the updates are working correctly...