side project a part 1: building xnu

I started to follow some instructions on building xnu for os 10.3.x, but quickly ran into a snag with the IOKitUser package in 10.4.4 requiring some private headers for the fancy new hibernate support. I'm now attempting to use darwinbuild as it looks a little more streamlined, and was struck by this suggestion:

"The build directory contains a hierarchy of directories that DarwinBuild uses while building Darwin projects. Since some sources require a case sensitive filesystem to build successfully (e.g. cvs), it's recommended to create your build directory on a case-sensitive HFSX or UFS volume."

great! some things don't run on case-sensitive filesystems, and some things don't run on case-insensitive filesystems. everything balances out in the end, and nothing runs =P.