Using json - Rasbats/shipdriver_pi GitHub Wiki
That is, if JavaScript_pi depends on libjsoncpp the build might fail. The remedy is then to add
add_subdirectory("libs/jsoncpp") target_link_libraries(${PACKAGE_NAME} ocpn::jsoncpp)
to the add_plugin_libraries macor in Plugin.cmake. And it actually makes sense: The plugin pulls in the libraries it needs.