mbootpack Makefile error

On my x86-64 Gentoo system, the xen-unstable compile breaks in tools/misc/mbootpack. It complains about not being able to find errno.h and page.h. After some digging (and help from Anthony, Jerone, and Scott), I found out that Gentoo's /usr/include/asm/errno.h errouniously has
#include "../asm-x86_64/errno.h"
instead of
#include <asm-generic/errno.h>

I am reporting the bug to Gentoo, but until this bug is fixed the patch below is needed. It removes the "-I-", which prevented gcc from using user include files.

Scott and Jerone verified that the header files in Ubuntu and Fedora do not have this file, though this may be a problem in SuSE (unable to confirm). Gentoo on x86 does not have the same /usr/include/asm/errno.h, so this is not an issue.

@@ -17,7 +17,7 @@ install: build
 #  Tools etc.
 RM 	:= rm -f
 GDB	:= gdb
-INCS	:= -I. -I-
+INCS	:= -I. 
 DEFS	:= 
 LDFLAGS	:= 
 CC	:= gcc