Make CI create deb, msi, and dmg files instead of tarballs/zips

[dfellis]

Lower priority, but we should be producing proper installers for Alan instead of relying on the user to extract the executable to the right location.

I've done a deb in the past, so I know it's just slapping a bunch of shell scripts together, but I have no experience with the msi or dmg formats except as a user for them, so we'll need to research how to do this. I fear we'll need to pay for an Apple developer account to do dmg based on what I've been reading: https://www.wikihow.com/Install-Software-from-Unsigned-Developers-on-a-Mac

[LoPoHa]

Once the FFI is implemented, it should be possible to write 'alanup' (an alan toolchain manager like rustup, ponyup, ...) to manage the installation of (different) alan version(s).
IMO this is better than having to manage the installation yourself.

rustup removed the msi installer and only uses an .exe installer (for itself). (see: rust-lang/rustup#1666), and installs rust from tar files afaik.