OSX_CURRENT_VERSION
-------------------

What current version number is this target for OSX.

For shared libraries on Mach-O systems (e.g. macOS, iOS)
the :prop_tgt:`OSX_COMPATIBILITY_VERSION` property correspond to
``compatibility version`` and ``OSX_CURRENT_VERSION`` to ``current version``.
See the :prop_tgt:`FRAMEWORK` target property for an example.

Versions of Mach-O binaries may be checked with the ``otool -L <binary>``
command.  If ``OSX_CURRENT_VERSION`` is not set, the value of
the :prop_tgt:``VERSION`` property will be used.