Xcode: Add support for shared library versioning

Add a post-build command to shared library targets to create the
versioning symbolic links.
Merge topic 'xcode-shlib-versioning' into next

cbe3f20 Xcode: Add support for shared library versioning
Add visibility flags when using xcode if needed.
Merge topic 'VISIBILITY_PRESET-property' into next

967b386 Add visibility flags when using xcode if needed.