(Initial Options): Document that -q disables customizations saving.

man/cmdargs.texi

@@ -200,7 +200,9 @@ explicitly requested.
 @cindex init file, not loading
 @cindex @file{default.el} file, not loading
 Do not load your Emacs init file @file{~/.emacs}, or @file{default.el}
-either.
+either.  When invoked like this, Emacs does not allow to save options
+changed with the @kbd{M-x customize} command and its variants.
+@xref{Easy Customization}.
 
 @item --no-site-file
 @opindex --no-site-file