Make sure zip module is loaded

Before we check for zip:foldl/3 make sure zip module is loaded.

src/rebar_utils.erl

@@ -116,6 +116,7 @@ abort(String, Args) ->
 %% this function when the time is right. escript:foldl/3 was an
 %% undocumented exported fun and is going to be removed post-R13B04.
 escript_foldl(Fun, Acc, File) ->
+    {module, zip} = code:ensure_loaded(zip),
     case erlang:function_exported(zip, foldl, 3) of
         true ->
             emulate_escript_foldl(Fun, Acc, File);