is it possible to build a cross toolchain for rust and llvm for bare metal thumbv8m.main-none-eabihf (ie raspberry pi pico 2) within nixpkgs from source
i patched lib/systems/parse.nix to allow "thumbv8m.main" as a cpu and i'm trying

crossSystem = {
  config = "thumbv8m.main-none-eabihf";
  libc = "newlib";
  useLLVM = true;
  rust.rustcTarget = "thumbv8m.main-none-eabihf";
};

and then attempting to build buildPackages.rustc and i'm immediately running into errors building compiler-rt

i can post logs/a complete example but like my first question is whether this is a path worth following at all? has anyone ever done something like this?