mainProgram
Changelog: https://git.sr.ht/~novakane/rivercarro/refs/v0.3.0
This makes using specific versions of zig easier (without overrides)
Also, a cosmetic refactor: - Reorder parameter listing - Use rec-less, overlay-style overridable recursive attributes (in effect since NixOS#119942); - Remove nested with (according to https://nix.dev/recipes/best-practices#with-scopes)