Makefile: Fix message for missing configure

When make is called without a valid configuration,
it should tell the user what to do.

Revision 0e8c9214
was a regression which resulted in a message
which was no longer user friendly
(reported by Aurelien Jarno).

This patch restores the old behaviour.

Cc: Aurelien Jarno <aurelien@aurel32.net>
Reviewed-by: NAndreas Färber <afaerber@opensolaris.org>
Signed-off-by: NStefan Weil <weil@mail.berlios.de>
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>

Makefile

@@ -75,7 +75,9 @@ SUBDIR_RULES=$(patsubst %,subdir-%, $(TARGET_DIRS))
 subdir-%: $(GENERATED_HEADERS)
 	$(call quiet-command,$(MAKE) $(SUBDIR_MAKEFLAGS) -C $* V="$(V)" TARGET_DIR="$*/" all,)
 
+ifneq ($(wildcard config-host.mak),)
 include $(SRC_PATH)/Makefile.objs
+endif
 
 $(common-obj-y): $(GENERATED_HEADERS)
 $(filter %-softmmu,$(SUBDIR_RULES)): $(common-obj-y)