undmg: use file name instead of pipe

There’s some issue in really big files with pipes that doesn’t occur
in filename decompression.

pkgs/tools/archivers/undmg/setup-hook.sh

···
 unpackCmdHooks+=(_tryUnpackDmg)
 _tryUnpackDmg() {
     if ! [[ "$curSrc" =~ \.dmg$ ]]; then return 1; fi
-    undmg < "$curSrc"
+    undmg "$curSrc"
 }