Fix undefined ipi_spec_dst for cygwin build.
The 'struct in_pktinfo' doesn't have a 'ipi_spec_dst' field on windows
OS which break cygwin builds of OpenSSL.
@@ -1125,7 +1125,9 @@ static int pack_local(BIO *b, MSGHDR_TYPE *mh, const BIO_ADDR *local) {
cmsg->cmsg_type = IP_PKTINFO;
info = (struct in_pktinfo *)BIO_CMSG_DATA(cmsg);
+# if !defined(OPENSSL_SYS_WINDOWS) && !defined(OPENSSL_SYS_CYGWIN)
info->ipi_spec_dst = local->s_in.sin_addr;
+# endif
info->ipi_addr.s_addr = 0;
info->ipi_ifindex = 0;
