kbuild: fix make O=...

kbuild failed to locate Kbuild.include.
Teach kbuild how to find Kbuild files when using make O=...
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
---

Makefile

@@ -310,7 +310,7 @@ cc-version = $(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-version.sh \
 MAKEFLAGS += --include-dir=$(srctree)
 
 # We need some generic definitions
-include scripts/Kbuild.include
+include  $(srctree)/scripts/Kbuild.include
 
 # For maximum performance (+ possibly random breakage, uncomment
 # the following)

scripts/Makefile.build

@@ -10,7 +10,9 @@ __build:
 # Read .config if it exist, otherwise ignore
 -include .config
 
-include $(if $(wildcard $(obj)/Kbuild), $(obj)/Kbuild, $(obj)/Makefile)
+# The filename Kbuild has precedence over Makefile
+include $(if $(wildcard $(srctree)/$(src)/Kbuild), \
+                        $(srctree)/$(src)/Kbuild, $(srctree)/$(src)/Makefile)
 
 include scripts/Kbuild.include
 include scripts/Makefile.lib

scripts/Makefile.clean

@@ -7,7 +7,9 @@ src := $(obj)
 .PHONY: __clean
 __clean:
 
-include $(if $(wildcard $(obj)/Kbuild), $(obj)/Kbuild, $(obj)/Makefile)
+# The filename Kbuild has precedence over Makefile
+include $(if $(wildcard $(srctree)/$(src)/Kbuild), \
+                        $(srctree)/$(src)/Kbuild, $(srctree)/$(src)/Makefile)
 
 # Figure out what we need to build from the various variables
 # ==========================================================================