kbuild: Fix menuconfig/xconfig and a modversions problem

If we are to build menuconfig/xconfig, we may not have a .config
yet, so we shouldn't try to include it.

Set MODVERDIR before including the subdir Makefile, drivers/scsi/53c700
needs it.

Makefile

@@ -211,7 +211,7 @@ SUBDIRS		:=
 
 ifeq ($(filter $(noconfig_targets),$(MAKECMDGOALS)),)
 
-include-config := 1
+export include-config := 1
 
 -include .config
 

scripts/Makefile.build

@@ -7,7 +7,9 @@ src := $(obj)
 .PHONY: __build
 __build:
 
+ifdef include-config
 include .config
+endif
 
 include $(obj)/Makefile
 

scripts/Makefile.modver

@@ -4,6 +4,8 @@
 
 src := $(obj)
 
+MODVERDIR := include/linux/modules
+
 .PHONY: modver
 modver:
 
@@ -28,8 +30,6 @@ else
 # This sets version suffixes on exported symbols
 # ---------------------------------------------------------------------------
 
-MODVERDIR := include/linux/modules
-
 #
 # Added the SMP separator to stop module accidents between uniprocessor
 # and SMP Intel boxes - AC - from bits by Michael Chastain