Since fontconfig by default generates font cache files in directories where
this port installs charmaps, try to remove them upon uninstallation, so
removing of directories has a chance to succeed. Just in case some user
has for some reason put fonts under these directories, be nice and try to
regenerate cache file and remove it again only if it is empty.
Pointed out by: pointyhat via kris
Approved by: portmgr (kris)