gnu-utility: avoid overriding shell builtins

Fixes #1263

modules/gnu-utility/init.zsh

@@ -48,7 +48,7 @@ _gnu_utility_cmds=(
 # Wrap GNU utilities in functions.
 for _gnu_utility_cmd in "${_gnu_utility_cmds[@]}"; do
   _gnu_utility_pcmd="${_gnu_utility_p}${_gnu_utility_cmd}"
-  if (( ${+commands[${_gnu_utility_pcmd}]} )); then
+  if (( ${+commands[${_gnu_utility_pcmd}]} && ! ${+builtins[${_gnu_utility_cmd}]} )); then
     eval "
       function ${_gnu_utility_cmd} {
         '${commands[${_gnu_utility_pcmd}]}' \"\$@\"