[tlbuild] TeX Live builds via Github - Solaris done

[Mojca Miklavec]

Dear Norbert,

Awesome job!

Two questions:
- Does it work if you select 12.4 as the FreeBSD release?
- Was there any good reason for selecting gcc 5.5 on Solaris? I only
used it because OpenCSW doesn't provide anything newer. If you build
on 11.4, I assume you can easily use a newer one.

> That leaves NetBSD, Darwin, Windows, Cygwin open ...

Cygwin might be doable on a Windows builder via this action:
    https://github.com/marketplace/actions/install-cygwin

You've had some nice experiences with NetBSD ;)

Windows is theoretically nicely supported via GitHub actions, but TeX
Live doesn't provide an out-of-the-box solution for building Windows
binaries. Akira does all the configuration more or less by hand.
(The other solution would be to add support for mingw cross-compiler,
but I would only use that for testing, not so much for actually
fetching the final binaries from there.)

Darwin-legacy requires a very old OS that isn't supported via GitHub
actions, so I'm not sure how to do that, even though it would be
awesome if there was a way.

Mojca