If a port requires xorg-server's source tree, how to write Makefile?

[meta]

Hi,

A few times I've already posted freebsd-ports list that I'm working for
creating a port net/tigervnc. It is almost be done  but I have a 
question.

TigerVNC's source tree is not complete to make everything.  We have to
put freebsd-patched xorg-server's source tree into its tree. I tried
like this. It builds fine with WITH_NEW_XORG and old xorg.

Is this a bad idea? Should I take another way?

post-extract:
   ${MAKE} -C ../../x11-servers/xorg-server patch
   ${CP} -R 
../../x11-servers/xorg-server/work/xorg-server-${XORG_VERSION}/* \
            ${WRKSRC}/unix/xserver/

post-clean:
   ${MAKE} -C ../../x11-servers/xorg-server clean


This tarball is my temporary working port.
http://www.club.kyutech.ac.jp/~meta/temp/tigervnc-port.tar.gz

-- 
`whois vmeta.jp | nkf -w`
meta <meta at vmeta.jp>

TigerVNC project is to merge enhancements of all different VNCs and
has unity in mind. For further information. Please see:
http://article.gmane.org/gmane.network.tight-vnc.general/8610/