DEFAULT_VERSIONS+= ssl=libressl
したいけど、www/squid がまだ security/libressl をサポートしてない

>Squid 4.7 release notes
>This release does not support LibreSSL. Due to a bug in the way LibreSSL uses the OpenSSL version macro some changes necessary to support OpenSSL 1.1 prevent building with LibreSSL.