fix Windows makefile
fix Windows makefile

yunxing/ocaml,gerdstolpmann/ocaml,yunxing/ocaml,eliberis/ocaml,eliberis/ocaml,msprotz/ocaml,yunxing/ocaml,yunxing/ocaml,msprotz/ocaml,msprotz/ocaml,yunxing/ocaml,gerdstolpmann/ocaml,msprotz/ocaml,eliberis/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,msprotz/ocaml,eliberis/ocaml,eliberis/ocaml