LIB: speed up copyDir

Instead of using zipLazy (which does more IO than we need)
we just construct the newDest zipper from the information we
already have. This should be sufficient.

src/IO/File.hs

@@ -108,7 +108,7 @@ copyDir :: DirCopyMode
         -> DTInfoZipper  -- ^ source dir
         -> DTInfoZipper  -- ^ destination dir
         -> IO ()
-copyDir cm from@(Dir fn _ _, _) to@(Dir {}, _) = do
+copyDir cm from@(Dir fn _ _, _) to@(tod@Dir {}, tobs) = do
   let fromp = getFullPath from
       top   = getFullPath to
       destdir = getFullPath to </> fn
@@ -120,7 +120,8 @@ copyDir cm from@(Dir fn _ _, _) to@(Dir {}, _) = do
 
   createDestdir destdir
 
-  newDest <- zipLazy mkDirInfo mkFileInfo destdir
+  ddinfo <- mkDirInfo destdir
+  let newDest = (Dir fn [] ddinfo, tod : tobs)
 
   for_ (goAllDown from) $ \f ->
     -- TODO: maybe do this strict?