openssl3: build failure on macOS 10.8

[mascguy (Christopher Nielsen)]

I'm seeing the following build failure on my macOS 10.8 VM, with Xcode/CLT 5.1.1:

SPECIFIC ERRORS - AND A COMPLETE ATTACHED BUILD LOG - TO BE ADDED SHORTLY

Note that updating the portfile to blacklist older Xcode clangs solves the issue.

However, given that our 10.8 buildbot is running Xcode 5.1.1 as well - and builds succeed there - thus far I've chalked it up to quirks in my particular 10.8 setup.

Also of note, this port builds successfully on every one of my other macOS VMs - including 10.6 and 10.7, as well as 10.9 through 10.15. It also builds successfully on my physical installations, for 10.12 through 10.15.