chat is this a normal *System.rust

    rust = {
      platform = builtins.fromJSON (builtins.readFile "${./rust}/mips64el_mips3-unknown-linux-gnuabi64.json");
      rustcTargetSpec = "${./rust}/mips64el_mips3-unknown-linux-gnuabi64.json";
      # cargoShortTarget = "mips64el_mips3-unknown-linux-gnuabi64";
      rustcTarget = "mips64el_mips3-unknown-linux-gnuabi64";
    };