Use SUPPORTED file for locale options

[codefiles]

Fixes #2041

[Torxed]

Looks good, just add glibc to https://github.com/archlinux/archinstall/blob/master/PKGBUILD#L13 and I'll merge it to the upstream package.

[codefiles]

Just a reminder that the PKGBUILD change has not been merged upstream. I also want to add that glibc should have already been in the dependency list of the PKGBUILD since locale-gen, which is from that package, is being used.

[Torxed]

On it, thanks for the reminder :) Just got back from a trip, so will begin packaging (and updating upstream) soon.
And yea, there's a few missing direct deps in the PKGBUILD, I started making it more accurate by adding the direct commands we execute but haven't made the list perfect.
If we find any more, feel free to add them :)