libtool: link: `/usr/local/lib/libxcb-xlib.la' is not a valid libtool archive
Of course, I've missed reading /usr/ports/UPDATING, where I could find that on 2009-01-23:
Libxcb shared library version was bumped from 1 to 2. You need to
rebuild any consumer of libxcb.so.1 or some applications will be
linked against two versions of libxcb once libX11 is upgraded.
For portupgrade users:
# portupgrade -rf libxcb