Rust supports musl and a bunch of BSDs, so if something broke with their packages, it should be only a matter of fixing the builds. That's a much smaller problem than adding a new old architecture to LLVM and rustc.
It's not just about adding new architectures to LLVM and rustc, it's also about bootstrapping supported architectures on all architectures supported by a distribution.
This isn't fully done in Alpine yet, and took a long time to do in Debian.
