Generally speaking, CMake libraries that are intended for use elsewhere will install an exports file - usually in ${INSTALL_DIR}/cmake/<project>Config.cmake - in order to allow third party CMake projects to locate the library with find_package(<project>). WIL does not appear to provide this CMake configuration file, and so it is unclear how the user is expected to integrate it into other CMake projects, and means that CMake projects that would otherwise use find_package() to pull in their dependencies now need to provide custom logic for WIL.

Now, it appears to me that CMake is not strictly used to package the library itself, but rather to do the packaging and testing tasks. I think the library would be well served with an exported interface library target which we could then pull in much more easily.