Avoids blocking on stdout.
The library does not depend on stdenv, that `stdenv` exposes `lib` is an artifact of the ancient origins of nixpkgs.
The old Quake3 NixOS test was removed in 50ea99cbc18d3f480a773de5250b4ef9c7f6d514 which served as a nice demo to showcase what NixOS tests are capable of. This commit adds the same functionality to run real openarena clients.