mod_enum: fix race condition between ldns configure creating ldns/util.h and mod_enum

Unbreaking make -jX parallel builds...
Signed-off-by: Stefan Knoblich <s.knoblich@axsentis.de>

src/mod/applications/mod_enum/Makefile

@@ -18,3 +18,4 @@ $(LDNS_LA): $(LDNS_BUILDDIR)/Makefile
 	cd $(LDNS_BUILDDIR) && $(MAKE)
 	$(TOUCH_TARGET)
 
+$(MODNAME).lo: $(LDNS_LA)