[PATCH] kbuild: build TAGS problem with O=

For inclusion into 2.6.12.stable, extracted from current Linus git:

[PATCH] kbuild: build TAGS problem with O=

  make O=/dir TAGS

  fails with:

    MAKE   TAGS
  find: security/selinux/include: No such file or directory
  find: include: No such file or directory
  find: include/asm-i386: No such file or directory
  find: include/asm-generic: No such file or directory

  The problem is in this line:
  ifeq ($(KBUILD_OUTPUT),)

KBUILD_OUTPUT is not defined (ever) after make reruns itself.  This line is
used in the TAGS, tags, and cscope makes.
Signed-off-by: George Anzinger <george@mvista.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

Makefile

@@ -1149,7 +1149,7 @@ endif # KBUILD_EXTMOD
 #(which is the most common case IMHO) to avoid unneeded clutter in the big tags file.
 #Adding $(srctree) adds about 20M on i386 to the size of the output file!
 
-ifeq ($(KBUILD_OUTPUT),)
+ifeq ($(src),$(obj))
 __srctree =
 else
 __srctree = $(srctree)/