bin/brew: unset functions that override builtins

Also, enable all Bash builtins

bin/brew

@@ -19,6 +19,13 @@ symlink_target_directory() {
   quiet_cd "$directory" && quiet_cd "$target_dirname" && pwd -P
 }
 
+for cmd in $(compgen -A builtin)
+do
+  unset -f $cmd  # Unset functions that override Bash builtins
+  enable $cmd # Enable all Bash builtins
+done
+unset cmd
+
 BREW_FILE_DIRECTORY="$(quiet_cd "${0%/*}/" && pwd -P)"
 HOMEBREW_BREW_FILE="${BREW_FILE_DIRECTORY%/}/${0##*/}"
 HOMEBREW_PREFIX="${HOMEBREW_BREW_FILE%/*/*}"