netboot: disable parallel build

pkgs/tools/networking/netboot/default.nix

···
 
   hardeningDisable = [ "format" ];
 
+  # Disable parallel build, errors:
+  #  link: `parseopt.lo' is not a valid libtool object
+  enableParallelBuilding = false;
+
   meta = with lib; {
     description = "Mini PXE server";
     maintainers = [ maintainers.raskin ];