When building ports in PC-BSD 7.2 I often get this error:
autom4te: need GNU m4 1.4 or later: /usr/local/bin/gm4
The actual cause is that /usr/local/bin/gm4 does not exist in PC-BSD. PC-BSD places it in /PCBSD/usr/local/bin/gm4. All you need to do is symlink it, and everything should build fine:
ln -s /PCBSD/local/bin/gm4 /usr/local/bin/gm4