copy graphics_file_rules.mk from emerald and modify Makefile to get multi-graphic-sprites working

Makefile

@@ -88,6 +88,8 @@ clean: tidy
 tidy:
 	rm -f $(ROM) $(ELF) $(MAP)
 	rm -r build/*
+	
+include graphics_file_rules.mk
 
 %.s: ;
 %.png: ;