'/cd,' is an undocumented option that seems to have the same effect as
'/root,'.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=48816.
Signed-off-by: Zhiyi Zhang <zzhang@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>