security/openvpn Mark a failing build with LibreSSL "IGNORE"

MFH: r506516

OpenVPN won't compile with LibreSSL, mark IGNORE.

Upstream maintainers are massively pushing back against patches
offered so far with valid and concrete technical reasons and unsuitability
of the LibreSSL version API that will create a maintenance nightmare.
(And LibreSSL abusing the OpenSSL API.)

Invoking blanket approval since this just marks a non-default configuration
that is failing "IGNORE", and changes a _DESC.

PR: 238382
Submitted by: pizzamig

Approved by: ports-secteam (blanket)