libpthread.so.1 - where to get it?

[Streiner, Justin]

I'm in the process of building a new system on freebsd 5.2.1.  Several X11
packages, such as the newest version of Mozilla Firefox complain about not
being able to find libpthread.so.1 when I try to run them.

I found libpthread.so.0 in my linux compatibility tree and did a fresh
portupgrade of linux_base and everything underneath it, but I still don't
have libpthread.so.1.  What do I need to install/build to get this
library?

Thanks
jms