!fixup Expose the Win32 logic in OpamStd.Sys.split_path

src/core/opamStd.ml

@@ -719,7 +719,7 @@ module OpamString = struct
       else
       let c = path.[index]
       and next = succ index in
-      if c = sep && normal || c = '"' then
+      if (c : char) = sep && normal || c = '"' then
         let current = current ^ String.sub path last (index - last) in
         if c = '"' then
           f acc next current next (not normal)