Ensure interfaces.manifest directory exists

The interfaces.manifest build script fails the target directory does not exist. This ensures
the target directory exists before attempting to build it.

Change-Id: Ib187b917bc8e4b70aa2ebe754a6feb1cd747441f

patch/all/build/xpcom.mk

@@ -144,6 +144,7 @@ LOCAL_ADDITIONAL_INSTALL_DEPENDENCIES += $(LOCAL_MODULE_PATH)/interfaces.manifes
 
 $(LOCAL_MODULE_PATH)/interfaces.manifest: PRIVATE_LOCAL_MODULE := $(LOCAL_MODULE)
 $(LOCAL_MODULE_PATH)/interfaces.manifest: $(GECKO_DIR)/config/buildlist.py
+	@mkdir -p $(@D)
 	$(PYTHON) $(GECKO_DIR)/config/buildlist.py $@ "interfaces $(PRIVATE_LOCAL_MODULE).xpt"
 endif