Bug 231286 - "make install" doesn't create directories for default pref files. r=bryner

config/rules.mk

@@ -1265,7 +1265,7 @@ endif
 endif
 
 ifndef NO_INSTALL
-install:: $(PREF_JS_EXPORTS)
+install:: $(PREF_JS_EXPORTS) $(DESTDIR)$(mozappdir)/$(PREF_DIR)
 	$(EXIT_ON_ERROR)  \
 	for i in $(PREF_JS_EXPORTS); \
 	do $(PERL) $(topsrcdir)/config/preprocessor.pl $(DEFINES) $(ACDEFINES) $$i > $(DESTDIR)$(mozappdir)/$(PREF_DIR)/`basename $$i`; \