os/utils.c: Don't try to build os_move_fd() for WIN32

Signed-off-by: Colin Harrison <colin.harrison@virgin.net>
Reviewed-by: Jon TURNEY <jon.turney@dronecode.org.uk>
(cherry picked from commit a9b4b7b796)

os/utils.c

@@ -2091,6 +2091,7 @@ FormatUInt64Hex(uint64_t num, char *string)
     string[len] = '\0';
 }
 
+#if !defined(WIN32) || defined(__CYGWIN__)
 /* Move a file descriptor out of the way of our select mask; this
  * is useful for file descriptors which will never appear in the
  * select mask to avoid reducing the number of clients that can
@@ -2114,3 +2115,4 @@ os_move_fd(int fd)
     close(fd);
     return newfd;
 }
+#endif