include(FetchContent) set(JSON_MultipleHeaders OFF) FetchContent_Declare( json GIT_REPOSITORY https://github.com/ArthurSonzogni/nlohmann_json_cmake_fetchcontent.git GIT_TAG 67e6070f9d9a44b4dec79ebe6b591f39d2285593 GIT_PROGRESS TRUE ) message("json") FetchContent_MakeAvailable(json)