This is not the way to do it.
This violates nix’ model and assumptions. This little environment variable can break nix packaged software.
If a program from nixpkgs requires this as a “fix”, it is broken and an issue/PR into nixpkgs is appreciated.
If this is for your software which you want to continue using at NixOS, you need to package it and “install” that package the proper way.
If this is for something you are developing, please use nix’ “development shells”.