minimal-bootstrap: Support `passthru.tests`

      passthru = attrs.passthru or {};

      validity = checkMeta.assertValidity { inherit meta attrs; };

      meta = checkMeta.commonMeta { inherit validity attrs; };

      baseDrv = derivation ({

        inherit (buildPlatform) system;

        inherit (meta) name;

      } // (builtins.removeAttrs attrs [ "meta" "passthru" ]));

      passthru' = passthru // lib.optionalAttrs (passthru ? tests) {

        tests = lib.mapAttrs (_: f: f baseDrv) passthru.tests;

      };

    in

    lib.extendDerivation

      validity.handled

      ({ inherit meta passthru; } // passthru)

      (derivation ({

        inherit (buildPlatform) system;

        inherit (meta) name;

      } // (builtins.removeAttrs attrs [ "meta" "passthru" ])));

      ({ inherit meta; passthru = passthru'; } // passthru')

      baseDrv;

  writeTextFile =

    { name # the name of the derivation