I don't know about other versions, but with gentoo-sources-2.6.18-r5, my attempt to "make headers_install" failed quickly with treat linux # make headers_install CHK include/linux/version.h make: unifdef: Command not found make: *** [headers_install] Error 127 I was doing this just to see what it was, but it seems to me if it appears in the output of "make help" it ought to work better than this. I'm omitting "emerge --info", expecting it to be immaterial. The kernel should be pretty much self-contained. I am running a completely current stable x86.
emerge dev-util/unifdef if you really need to do this...