With the default (-Dxvfb=true), Xvfb is built but not installed. So
leave the default (as Xvfb may be used in test), and add instruction to
install it if the user won't use xorg-server.
- create the /tmp/.X11-unix directory with permission 1777 using
/etc/sysconfig/createfiles
- add pam_loginuid.so as required in /etc/pam.d/gdm-launch-environment
- ensure /etc/X11/xorg.conf.d exists after installing xwayland (both
sysv and systemd)