Integrate with Cosmopolitan to get a portable executable

[hans-helmut]

Feature Request: integrate https://github.com/jart/cosmopolitan and create an executable, that runs on all three supported operating systems.

[rzane]

I love this idea, but I don't have a lot of experience with Cosmopolitan. If someone would be willing to put together a pull request, I'd happily merge it. Ideally, you'd opt-in to this functionality using a command line option.