Mainly this is following Linux to build own xml2/lzma/ssl/sqlite and linking
them all statically. This ensures the Python ssl module uses a recent openssl
version rather than a very old one shipped with macOS.
Note these are intended for platform maintainers, we do not intend to
support users making their own builds with these. For that precompiled
libraries from lib/ should be used.
Implemented by Martijn Berger, Ray Molenkamp and Brecht Van Lommel.
Differential Revision: https://developer.blender.org/D2753