The "unset MODULE_DIR" trick was enough to get Linux 3.x kernels compiling, but it was definitely the Wrong Thing
We NEED MODULE_DIR set so that depmod can store the right dependencies during the build. The REAL problem with the
3.x kernels was two-fold: Our module-init-tools was so old that the kernel build needed to introduce a hack when
calling depmod (involving creating a symlink prepending 99.98 to the version number), and the depmod wrapper was
moved out of the Makefile into scripts/depmod.sh, so our substituteInPlace to get rid of '-b $(INSTALL_MOD_PATH)' in
the Makefile was a noop and INSTALL_MOD_PATH was still being passed to depmod. This is now fixed and modprobe can
successfully find dependencies using the modules.dep created during install
svn path=/nixpkgs/trunk/; revision=29559
34144e835d