kbuild: make sure autoksyms.h exists early

Some people are able to trigger a race where autoksyms.h is used before
its empty version is even created.  Let's create it at the same time as
the directory holding it is created.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Tested-by: Prarit Bhargava <prarit@redhat.com>
Tested-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: Nicolas Pitre

Makefile

@@ -1019,8 +1019,6 @@ prepare2: prepare3 prepare-compiler-check outputmakefile asm-generic
 prepare1: prepare2 $(version_h) include/generated/utsrelease.h \
                    include/config/auto.conf
 	$(cmd_crmodverdir)
-	$(Q)test -e include/generated/autoksyms.h || \
-	    touch   include/generated/autoksyms.h
 
 archprepare: archheaders archscripts prepare1 scripts_basic
 

scripts/kconfig/Makefile

@@ -35,6 +35,8 @@ nconfig: $(obj)/nconf
 
 silentoldconfig: $(obj)/conf
 	$(Q)mkdir -p include/config include/generated
+	$(Q)test -e include/generated/autoksyms.h || \
+	    touch   include/generated/autoksyms.h
 	$< $(silent) --$@ $(Kconfig)
 
 localyesconfig localmodconfig: $(obj)/streamline_config.pl $(obj)/conf