XFree86-4 won't build on 4.9

[Peter Jeremy]

I've just wiped all my packages to do a clean rebuild and it has
failed virtually at the start: With an up-to-date /usr/ports and
non-existent /etc/make.conf, XFree86-4 won't build on
4.9-approximately-RELEASE.

XFree86-libraries-4.3.0_6 appears to build and install OK but building a
package gives:
------------------
===>  Building package for XFree86-libraries-4.3.0_6
Creating package /usr/ports/packages/All/XFree86-libraries-4.3.0_6.tgz
Registering depends: fontconfig-2.2.90_4 expat-1.95.6_1 freetype2-2.1.5_2 imake-
4.3.0_2 pkgconfig-0.15.0_1.
Creating gzip'd tar ball in '/usr/ports/packages/All/XFree86-libraries-4.3.0_6.t
gz'
tar: lib/libXThrStub.so: Cannot stat: No such file or directory
tar: lib/libXThrStub.so.6: Cannot stat: No such file or directory
tar: Error exit delayed from previous errors
pkg_create: make_dist: tar command failed with code 512
*** Error code 1

Stop in /home/ports/x11/XFree86-4-libraries.
*** Error code 1

Stop in /home/ports/x11/XFree86-4.
-----------------

There is no libXThrStub.{a,so*} built or installed so the error isn't
surprising but why isn't libXThrStub.* being built?  Any ideas?

Please copy me on any responses.

Peter