Show HN: Group directories first with modified macOS `ls`

I finally got tired of not having directories first on macOS, and something like exa <https://the.exa.website/> seemed overkill.

So I dug into the source code, hunted down the missing BSD-licensed headers, figured out how to work around the APSL headers (reverse engineering is documented in the comments in print.c), and smoothed out some rough edges.

Very much a personal itch-scratching exercise, but I think this is something that bugs a lot of people, so hopefully it's useful!