Problem with virtualbox-ose-additions

Tue Sep 10 21:59:08 UTC 2013

I have upgraded to r255358, rebuilt world and kernel, and dealt with the 
iconv issues. In the process I had to delete a handful of ports, am now 
trying to reinstall them, and am running into a problem:

FreeBSD freebsd.vm 10.0-CURRENT FreeBSD 10.0-CURRENT #0 r255358: Sat Sep  
7 22:28:09 BST 2013     root at freebsd.vm:/usr/obj/usr/src/sys/VM10  amd64

virtualbox-ose-additions will not compile. I get:

kBuild: Linking VBoxOGLcrutil
/usr/bin/ld: cannot find -liconv

Have I done something wrong? How should I take this forward?