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]]