CheckCXXFeatures
----------------

This module checks for several CXX compiler features and introduces a macro to check if
given C++ source compiles and links into an executable.

.. cmake:command:: dune_check_cxx_source_compiles

  .. code-block:: cmake

    dune_check_cxx_source_compiles(<sources> <var>)

  The macro checks that the given sources compiles and links into an executable. Thus,
  it must at least provide a valid ``main()`` function. The macro is inspired by the
  CMake module command
  `check_cxx_source_compiles() <https://cmake.org/cmake/help/latest/module/CheckCXXSourceCompiles.html#command:check_cxx_source_compiles>`_
  but does not provide all of its functionality. It is also based on the
  :dune:cmake-command:`try_compile` command but without any additional flags
  set, like include directories or link options. The only fixed flag that is
  passed to :dune:cmake-command:`try_compile` is
  `CXX_STANDARD <https://cmake.org/cmake/help/latest/prop_tgt/CXX_STANDARD.html>`_
  with value 17. This can only be influenced by setting the global variable
  `CMAKE_CXX_STANDARD <https://cmake.org/cmake/help/latest/variable/CMAKE_CXX_STANDARD.html>`_.