get_directory_property
----------------------

Get a property of ``DIRECTORY`` scope.

.. code-block:: cmake

  get_directory_property(<variable> [DIRECTORY <dir>] <prop-name>)

Stores a property of directory scope in the named ``<variable>``.

The ``DIRECTORY`` argument specifies another directory from which
to retrieve the property value instead of the current directory.
Relative paths are treated as relative to the
current source directory.  CMake must already know about the directory,
either by having a                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   