The warning says:
CMake Deprecation Warning at .../CMakeLists.txt:1 (cmake_minimum_required):
Compatibility with CMake < 3.5 will be removed from a future version of
CMake.
Spotted by Scott Kostyshak
(cherry picked from commit 8d79860ea7)
The added cmake-parameter is:
-DLYX_EXTERNAL_MYTHES=<value>
where <value> is one of
AUTO (Default) Search first on system for mythes (lib and include)
ON Use installed only (errors if not installed)
OFF Compile the provided source in 3rdparty