Create local.conf in /usr/pkg/etc/fontconfig

<?xml version="1.0"?><!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig><include>conf.d/70-no-bitmaps.conf</include></fontconfig>

There referenced file "70-no-bitmaps.conf" doesn't exist in conf.d and therefore have to be copied there first.

# cp /usr/pkg/share/examples/fontconfig/conf.avail/70-no-bitmaps.conf /usr/pkg/etc/fontconfig/conf.d/

That's it. Now restart firefox. X11