nix develop and nixglhost don't work well together without separating args from program with `--`

The readme and help messages suggest using nixglhost like so ``` nixglhost my-gl-program args ``` I received errors trying to run ``` nixglhost R -e "print('hello')" ``` It worked when I changed the call to ``` nixglhost -- R -e "print('hello')" ``` For future users, knowing about `--` might be very useful.