clfswm: mark as broken

This package has been broken for quite a long time. I attempted
to fix it, to no avail.

See also: https://hydra.nixos.org/build/33498133/nixlog/2/raw

(cherry picked from commit 9ae0e6633edb0ac53edaa6d3970b7cacc1db7834)

pkgs/applications/window-managers/clfswm/default.nix

···
     license     = licenses.gpl3;
     maintainers = with maintainers; [ robgssp ];
     platforms   = platforms.linux;
+    broken      = true;
   };
 }