[PATCH] Makefile include path ordering

The arch Makefile may override the include path order, which is used by Xen
(and UML?) to make sure include/asm-xen is searched before
include/asm-i386.

The Makefile change to 2.6.12-rc4 made the top Makefile always override the
value specified by the arch Makefile.  This trivial patch makes the Xen
kernel compile again.
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Makefile

@@ -530,7 +530,7 @@ endif
 include $(srctree)/arch/$(ARCH)/Makefile
 
 # arch Makefile may override CC so keep this after arch Makefile is included
-NOSTDINC_FLAGS := -nostdinc -isystem $(shell $(CC) -print-file-name=include)
+NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include)
 CHECKFLAGS     += $(NOSTDINC_FLAGS)
 
 # warn about C99 declaration after statement