In the process of fixing another bug [1], I had no problem building from source. Could you try to reproduce with the patch I've included with that bug? It should change the svg importer to not try to use rsvg (though, I don't understand why it would try and fail).
Does /convert ultimately point to /usr/bin/convert-im6.q16? [1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=894653
