refactor(fun/wcl): Use portable unix-opts library

unix-opts, imported into buildLisp.nix in the previous commit,
provides an implementation independent way of parsing command line
arguments.

fun/wcl/default.nix

@@ -8,6 +8,7 @@ pkgs.nix.buildLisp.program {
   ];
 
   deps = with pkgs.third_party.lisp; [
+    unix-opts
     iterate
   ];
 }