Use the Universal Installer, NOT the Mac Installer. Follow the instructions on plone.org for installing with the Universal Installer

You'll get a base.cfg and a buildout.cfg, you can put everything into the buildout.cfg and ignore base.cfg

Make sure buildout picks up the correct versions (and trumps other specified versions, by putting the collective.xdv version set last of all)

extends =
    base.cfg
    versions.cfg
#    http://dist.plone.org/release/4.0.1/versions.cfg
    http://good-py.appspot.com/release/collective.xdv/1.0?plone=4.0.1

Add collective.xdv to the list of eggs

eggs =
    Plone
    PIL==1.1.6
    collective.xdv

Add an lxml part (to compile lxml, rather than rely on downloading an egg) to the top of the list of parts

parts =
    lxml
    osxcontroller    instance
    zopepy
    zopeskel
    unifiedinstaller
    chown

At the bottom of the buildout.cfg file add this extra lxml part

[lxml]
recipe = z3c.recipe.staticlxml
egg = lxml
libxml2-url = http://xmlsoft.org/sources/libxml2-2.7.7.tar.gz
libxslt-url = http://xmlsoft.org/sources/libxslt-1.1.26.tar.gz