Since kwin runs as a normal user, it cannot create the X11 connection
socket directory because any user process can easily compromise the
security of the system by unsetting the sticky bit.
In order to guarantee the security of the system, the socket directory
must be created by root and have the sticky bit on.
This provides kwin greater control over how X11 sockets are created for
Xwayland. For example, it can be used to ensure that the DISPLAY remains
the same across Xwayland server restarts or launching Xwayland on
demand.
Even though -listen <fd> option is deprecated, we still pass it because
older versions of Xwayland may not have the -listenfd option.
