generic/setup.sh: Unset locally defined variables
generic/setup.sh: Unset locally defined variables

setup.sh adds a bunch of variables that only it needs. To avoid
polluting environments, we should unset these as soon as we are done
with them.

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs