oom: add header file to Kbuild as unifdef

Preprocess include/linux/oom.h before exporting it to userspace.

Cc: Andrea Arcangeli <andrea@suse.de>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/Kbuild

@@ -283,6 +283,7 @@ unifdef-y += nfs_idmap.h
 unifdef-y += n_r3964.h
 unifdef-y += nubus.h
 unifdef-y += nvram.h
+unifdef-y += oom.h
 unifdef-y += parport.h
 unifdef-y += patchkey.h
 unifdef-y += pci.h