fix Windows makefile
fix Windows makefile

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