Oh, I get it. You're building from a directory with a space in it. That doesn't even work on Windows. Stop doing it.
"Doctor, it hurts when I do this." "Well, don't do that, then!" I may be no medical expert, but in this case I know I can do better than that. Anyway, it works now that I've fixed it, and I've submitted the pull request. Since the GENie license does allow modifications, I decided to apply the same patch I submitted to the GENie project, which means that sdl_cfg.lua can stay exactly as it was.