kbuild: fix silentoldconfig with make O=

Al Viro reported that sometimes silentoldconfig failed because
output directory was missing.
So create it unconditionally before executing conf

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

diff --git a/Makefile b/Makefile
index e90ee6a..45e5a38 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -491,6 +491,7 @@ include .config
 # If .config is newer than include/linux/autoconf.h, someone tinkered
 # with it and forgot to run make oldconfig
 include/linux/autoconf.h: .config
+       $(Q)mkdir -p include/linux
        $(Q)$(MAKE) -f $(srctree)/Makefile silentoldconfig
 else
 # Dummy target needed, because used as prerequisite