too many shell scripts

[ongardie]

The package definitions currently have a lot of shell scripts, which is bad for my sanity, as well as correctness and portability (across distros or versions of tools, or even operating systems). They're likely to get more complicated, too, thanks to #30, #31, #34, and #36.

It should be possible to use build_depends and write many of these scripts in a more suitable language. Rust is probably my top pick. It'd have challenges of convenience and compilation times, but I think we can find ways to overcome those.