-o doesn't exist on *BSD, so don't mention it

Fixes: debbugs:9301

lisp/ChangeLog

@@ -1,5 +1,8 @@
 2011-09-11  Lars Magne Ingebrigtsen  <larsi@gnus.org>
 
+	* dired.el (dired-sort-toggle-or-edit): -o doesn't exist on *BSD,
+	so don't mention it (bug#9301).
+
 	* faces.el (face-spec-set-match-display): Make `(type graphic)'
 	match `x', `w32' and `ns', like the manual says (bug#9029).
 

lisp/dired.el

@@ -3413,7 +3413,8 @@ With a prefix argument, edit the current listing switches instead."
     (error "Cannot sort this dired buffer"))
   (if arg
       (dired-sort-other
-       (read-string "ls switches (must contain -l, -o, or -g): " dired-actual-switches))
+       (read-string "ls switches (must contain -l or -g): "
+		    dired-actual-switches))
     (dired-sort-toggle)))
 
 (defun dired-sort-toggle ()