Darwin’s default LLVM version is 7, but there are much newer versions of even the open source compiler out. Why is the default a version that’s a couple of years old?
I think that the answer is that someone needs to put in the time to do the update. There is a PR for 7 → 9:
https://github.com/NixOS/nixpkgs/pull/85151
Though I guess that an update to a very recent LLVM will be necessary for AArch64 support on Darwin.
Well, fwiw, I put another pair of eyes on it for a bit. Didn’t see anything wrong, but then there are things (eg keeping packages back on 7) that I don’t have context for.