Fix build system

[jefdaj]

I have a hodgepodge of build setups "mostly working", but none that work in all situations:

• shell.nix + stack build builds the closest-to-static binary I've been able to achieve on MacOS
• shell.nix + stack build on Linux works but the binary has a lot of dynamic libs
• flake.nix static build works on Linux, but not on the latest ghc (9.8.1), and not with my dev dependencies in the shell

I'd like to migrate everything to the flake if possible, but need to wait for a couple issues to resolve themselves upstream or figure out how to work around them.