My personal implementation of std::optional/boost::optional, just for fun.
From the cmake directory, copy the FindLB directory to a place in your CMAKE_MODULE_PATH.
Then, add find_package(LB/optional REQUIRED) to your CMake script.
You may need to set the CMake variable LB/optional_ROOT if you installed to a nonstandard location.
Finally, link to the LB::optional imported target with target_link_libraries().
First #include <LB/optional/optional.hpp>, and then bug LB to finish this TODO.