Swap out Makefile with Go scripts

[jbduncan]

This is an experiment to see how far I can go with using Go to script everything, similar to Rust's approach to using an x.py script.

This is done partly out of fun and partly to allow linting to run tools concurrently without resorting to Bash trickery or installing GNU parallel (though it may be adopted anyway if Nix is adopted as a way of managing consistent versions of various tools).

Follow a similar approach to https://blog.kowalczyk.info/article/4b1f9201181340099b698246857ea98d/using-go-instead-of-bash-for-scripts.html.

However, make sure to use go build and run the script binary directly because the docs for go run say,

The exit status of Run is not the exit status of the compiled binary.

Consider using https://github.com/bitfield/script, the u-root userland binaries or Nix to use consistent and reproducible versions of any Unix tools that may be needed.

Related: #27.