RetroArch cores to enable. You can provide custom core packages.
attribute set of (submodule)
{ }
{ mgba.enable = true; # Uses pkgs.libretro.mgba snes9x = { enable = true; package = pkgs.libretro.snes9x2010; }; custom-core = { enable = true; package = pkgs.callPackage ./custom-core.nix { }; }; }