Change the logic so that when a user folder already exists in the
prefix, as a real directory or symbolic link, it's left as-is. Also
create a symbolic link, instead of a real directory, when looking up a
user folder that is currently missing.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=22974Signed-off-by: Olivier F. R. Dierick <o.dierick@piezo-forte.be>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>