By default, /usr/X11R6/lib/X11 /usr/X11/lib/X11 /usr/lib/X11 are added
if they exist at compile time
https://cgit.freedesktop.org/fontconfig/tree/configure.ac?id=b546940435ebfb0df575bc7a2350d1e913919c34#n502
We prefer isolation from base system

Remove the comment questioning about --add-default-font because we don't
add fonts for this reason and also because users can use a $FONTCONFIG
file.