How to set package cofigurations in nix packge without nixos

I have installed a Nix package on my ubuntu os, that depends on doas, and for it to function, it's binary need's to have the suid bit set - and it isn't in the default nix-env installation. On NixOS you can enable a suid wrapper for doas (nixos wiki ), but that has to be put into /etc/nixos/configuration.nix, which doesn't exist out of NixOS. Does anyone know how to set that configuration value or get doas to function in a different way