Since LibreSSL's libssl now exposes DTLS1_2_VERSION, configure detects DTLS support which changes the DTLSv1_listen(3) signature to one that LibreSSL has never supported. Force disable DTLS feature for SSL_DEFAULT=libressl or libressl-devel.
Based on: https://github.com/openbsd/ports/commit/9942e8d28c4ec59d8d4a20b8bf219b10573c1f31