Kbuild: arch: look for generated headers in obtree

There are very few files that need add an -I$(obj) gcc for the preprocessor
or the assembler. For C files, we add always these for both the objtree and
srctree, but for the other ones we require the Makefile to add them, and
Kbuild then adds it for both trees.

As a preparation for changing the meaning of the -I$(obj) directive to
only refer to the srctree, this changes the two instances in arch/x86 to use
an explictit $(objtree) prefix where needed, otherwise we won't find the
headers any more, as reported by the kbuild 0day builder.

arch/x86/realmode/rm/realmode.lds.S:75:20: fatal error: pasyms.h: No such file or directory

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Michal Marek <mmarek@suse.com>
diff --git a/arch/um/Makefile b/arch/um/Makefile
index e3abe6f..0ca46ede 100644
--- a/arch/um/Makefile
+++ b/arch/um/Makefile
@@ -78,8 +78,8 @@
 
 KBUILD_CPPFLAGS += -I$(srctree)/$(HOST_DIR)/include \
 		   -I$(srctree)/$(HOST_DIR)/include/uapi \
-		   -I$(HOST_DIR)/include/generated \
-		   -I$(HOST_DIR)/include/generated/uapi
+		   -I$(objtree)/$(HOST_DIR)/include/generated \
+		   -I$(objtree)/$(HOST_DIR)/include/generated/uapi
 
 # -Derrno=kernel_errno - This turns all kernel references to errno into
 # kernel_errno to separate them from the libc errno.  This allows -fno-common