I have explained in a previous post how the old version of msp430-gcc is getting depreciated everywhere. Now even the binaries are getting bit rot. So if msp430-gcc complains on FreeBSD that libmpfr.so.4 is missing, here is a quick dirty hack that you can use:

cd /usr/local/lib
ln -s libmpfr.so.6 libmpfr.so.4