musl with musl-gcc/musl-clang wrapper

musl.nix

   (musl.overrideAttrs (old: {
      configureFlags = (old.configureFlags or []) ++ ["--enable-wrapper=all"];
      preFixup = (old.preFixup or "") + ''
        for i in bin/{musl-gcc,musl-clang,ld.musl-clang}; do
          moveToOutput $i $dev
        done
        moveToOutput lib/musl-gcc.specs $dev
        substituteInPlace $dev/bin/musl-gcc \
          --replace $out/lib/musl-gcc.specs $dev/lib/musl-gcc.specs
      '';
    }))