`LON_OVERRIDE_*` confusion

more great software from @nikstur eh? ❤️

conceptually, i wonder what i am missing about `LON_OVERRIDE_*` - why is it being purposely copied to the nix store instead of just referenced locally?

i was so confused when i saw my `~/nixpkgs` clone was being copied to the store after setting `LON_OVERRIDE_nixpkgs=~/nixpkgs`

i would appreciate any explanations you can provide

thanks!