kbuild: make headerdep work in KBUILD_OUTDIR

This patch fixes the headerdep target so it works when make is invoked
in KBUILD_OUTDIR.

Signed-off-by: Peter Foley <pefoley2@verizon.net>
Signed-off-by: Michal Marek <mmarek@suse.cz>
1 file changed