kbuild: fix first module build

When building a specific module before doing a total kernel
build it failed because $(MORVERDIR) were missing.
Creating the MODVERDIR explicit (independent of KBUILD_MODULES)
fixed this. As a side-effect the MODVERDIR will be created
also for a non-module build - but no harm done by that.
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

Makefile

@@ -884,10 +884,7 @@ prepare2: prepare3 outputmakefile
 
 prepare1: prepare2 include/linux/version.h include/linux/utsrelease.h \
                    include/asm include/config/auto.conf
-ifneq ($(KBUILD_MODULES),)
-	$(Q)mkdir -p $(MODVERDIR)
-	$(Q)rm -f $(MODVERDIR)/*
-endif
+	$(cmd_crmodverdir)
 
 archprepare: prepare1 scripts_basic
 
@@ -1223,8 +1220,7 @@ else # KBUILD_EXTMOD
 KBUILD_MODULES := 1
 PHONY += crmodverdir
 crmodverdir:
-	$(Q)mkdir -p $(MODVERDIR)
-	$(Q)rm -f $(MODVERDIR)/*
+	$(cmd_crmodverdir)
 
 PHONY += $(objtree)/Module.symvers
 $(objtree)/Module.symvers:
@@ -1484,9 +1480,11 @@ endif
 
 # Modules
 / %/: prepare scripts FORCE
+	$(cmd_crmodverdir)
 	$(Q)$(MAKE) KBUILD_MODULES=$(if $(CONFIG_MODULES),1) \
 	$(build)=$(build-dir)
 %.ko: prepare scripts FORCE
+	$(cmd_crmodverdir)
 	$(Q)$(MAKE) KBUILD_MODULES=$(if $(CONFIG_MODULES),1)   \
 	$(build)=$(build-dir) $(@:.ko=.o)
 	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost
@@ -1510,6 +1508,9 @@ quiet_cmd_depmod = DEPMOD  $(KERNELRELEASE)
 		$(KERNELRELEASE);                                               \
 	fi
 
+# Create temporary dir for module support files
+cmd_crmodverdir = $(Q)mkdir -p $(MODVERDIR); rm -f $(MODVERDIR)/*
+
 
 a_flags = -Wp,-MD,$(depfile) $(KBUILD_AFLAGS) $(AFLAGS_KERNEL) \
 	  $(NOSTDINC_FLAGS) $(KBUILD_CPPFLAGS) \