maildrop port build/configure fail: failed for liblock

[Da Rock]

Quick question, one that hasn't come up since 2002 apparently; does 
anyone know what to do with this error when building maildrop?

checking whether setpgrp takes no argument... no
checking for fcntl... yes
checking for flock... yes
checking for lockf... yes
checking for locking method... configure: error: must specify 
--with-locking-method option
configure: error: ./configure failed for liblock
===>  Script "configure" failed unexpectedly.
Please report the problem to madpilot at FreeBSD.org [maintainer] and 
attach the
"<WRKDIRPREFIX>/usr/ports/mail/maildrop/work/maildrop-2.6.0/config.log"
including the output of the failure of your make command. Also, it might be
a good idea to provide an overview of all packages installed on your system
(e.g. a /usr/sbin/pkg_info -Ea).

Is there an easy fix for this that will sort it out immediately before I 
go and follow this method and wait a while for a solution?

This is a new install of 9.1 with a ports tree updated from svn a few 
days ago, my ports tree is on a zfs file server over nfs with rpcbind, 
lockd, statd, etc, and the WRKDIRPREFIX is set to another directory on 
the file server. Mount in the fstab is just server:/mount share /mount 
point nfs rw 0 0.

Any clues much appreciated.

Cheers