[PATCH] Avoid rebuild of IKCFG when using O=

When using a separate output directory the in-kernel config wiere rebuild
each time the kernel was compiled.  Fix this by specifying correct path to
Makefile in the prerequisite to the ikconfig.h file.
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

kernel/Makefile

@@ -48,7 +48,7 @@ quiet_cmd_ikconfig = IKCFG   $@
       cmd_ikconfig = $(CONFIG_SHELL) $< .config $(srctree)/Makefile > $@
 
 targets += ikconfig.h
-$(obj)/ikconfig.h: scripts/mkconfigs .config Makefile FORCE
+$(obj)/ikconfig.h: scripts/mkconfigs .config $(srctree)/Makefile FORCE
 	$(call if_changed,ikconfig)
 
 # config_data.h contains the same information as ikconfig.h but gzipped.