OSX: Building lxml

It seems that building lxml on Mac OS X is still a problem. I'm trying to use buildout as in:

[libxslt]
recipe = zc.recipe.cmmi
url = http://ftp.gnome.org/pub/GNOME/sources/libxslt/1.1/libxslt-1.1.16.tar.bz2
extra_options = --with-libxml-prefix=${buildout:directory}/parts/libxml2/
             --without-python

[lxml]
recipe = zc.recipe.egg:custom
egg = lxml
include-dirs = ${buildout:directory}/parts/libxml2/include/libxml2
            ${buildout:directory}/parts/libxslt/include
library-dirs = ${buildout:directory}/parts/libxml2/lib
            ${buildout:directory}/parts/libxslt/lib
rpath = ${buildout:directory}/parts/libxml2/lib
     ${buildout:directory}/parts/libxslt/lib

That fails when buildout tries to build the lxml egg. Looking closely at the error, I discovered that despite pointing it at the libxslt built, it still uses the one found in /usr/lib. To be more specific: lxml tries to find xslt-config, which is in $BO/parts/libxslt/bin/xslt-config, but of course finds the one in /usr/bin first. What I'd like to do is to add something like:

# this would be needed but zc.recipe.egg:custom doesn't allow for that
# Doh.
extra_options= --with-xslt-config=${buildout:directory}/parts/libxslt/bin/xslt-config

That option is available in zc.recipe.cmmi, but not in zc.recipe.egg. Looking at custom.py there I sadly found no obvious way to add this as it uses some version of easy_install. D'oh. Possible solutions:

• build egg manually, add to egg cache (yuck-bleah)
• build manually for OS X, add to own egg server (yuck)
• roll-my-own recipe (work)