{ lib, ... }:
with lib;
{
  config.outputKinds = [
    (
      { hasSystem, ... }:
      optionalAttrs (!hasSystem) {
        options = {
          overlays = mkOption {
            type = with types; attrsOf (functionTo (functionTo attrs));
            description = "Overlay, consumed by other flakes";
          };
        };
        outputs = { config, ... }: {
          overlays = config.overlays;
        };
      }
    )
  ];
}