kbuild: Fix bug in make deb-pkg when using seperate source and output directories

From: Ryan Anderson <ryan@michonline.com>

When running "make O=something deb-pkg", I get a failure that claims I
haven't configured my kernel (I have).  Running it a second time tells
me to run "make mrproper"  (include/linux/version.h got built on the
first run)

Original patch from:
From: Ajay Patel <patela@gmail.com>

With modifications from:
Signed-off-By: Ryan Anderson <ryan@michonline.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

scripts/package/Makefile

@@ -59,7 +59,7 @@ $(objtree)/binkernel.spec: $(MKSPEC) $(srctree)/Makefile
 	$(CONFIG_SHELL) $(MKSPEC) prebuilt > $@
 	
 binrpm-pkg: $(objtree)/binkernel.spec
-	$(MAKE)
+	$(MAKE) KBUILD_SRC=
 	set -e; \
 	$(CONFIG_SHELL) $(srctree)/scripts/mkversion > $(objtree)/.tmp_version
 	set -e; \
@@ -74,7 +74,7 @@ clean-files += $(objtree)/binkernel.spec
 #
 .PHONY: deb-pkg
 deb-pkg:
-	$(MAKE)
+	$(MAKE) KBUILD_SRC=
 	$(CONFIG_SHELL) $(srctree)/scripts/package/builddeb
 
 clean-dirs += $(objtree)/debian/