Kbuild: always prefix objtree in LINUXINCLUDE

When $(LINUXINCLUDE) is added to the cflags of a target that
normall doesn't have it (e.g. HOSTCFLAGS), each entry in the
list is expanded so that we search both $(objtree) and $(srctree),
which is a bit silly, as we already know which of the two we
want for each entry in LINUXINCLUDE.

Also, a follow-up patch changes the behavior so we only look in
$(srctree) for manually added include path, and that breaks finding
the generated headers.

This adds an explicit $(objtree) for each tree that we want to
look for generated files.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Michal Marek <mmarek@suse.com>

Makefile

@@ -375,19 +375,19 @@ CFLAGS_KCOV	:= $(call cc-option,-fsanitize-coverage=trace-pc,)
 # Use USERINCLUDE when you must reference the UAPI directories only.
 USERINCLUDE    := \
 		-I$(srctree)/arch/$(hdr-arch)/include/uapi \
-		-Iarch/$(hdr-arch)/include/generated/uapi \
+		-I$(objtree)/arch/$(hdr-arch)/include/generated/uapi \
 		-I$(srctree)/include/uapi \
-		-Iinclude/generated/uapi \
+		-I$(objtree)/include/generated/uapi \
                 -include $(srctree)/include/linux/kconfig.h
 
 # Use LINUXINCLUDE when you must reference the include/ directory.
 # Needed to be compatible with the O= option
 LINUXINCLUDE    := \
 		-I$(srctree)/arch/$(hdr-arch)/include \
-		-Iarch/$(hdr-arch)/include/generated/uapi \
-		-Iarch/$(hdr-arch)/include/generated \
+		-I$(objtree)/arch/$(hdr-arch)/include/generated/uapi \
+		-I$(objtree)/arch/$(hdr-arch)/include/generated \
 		$(if $(KBUILD_SRC), -I$(srctree)/include) \
-		-Iinclude
+		-I$(objtree)/include
 
 LINUXINCLUDE	+= $(filter-out $(LINUXINCLUDE),$(USERINCLUDE))