Don't install JSON libraries used for tests

    FetchContent_Populate(nlohmann_json)

    message(STATUS "[gkfs.io] Nlohmann JSON source dir: ${nlohmann_json_SOURCE_DIR}")

    message(STATUS "[gkfs.io] Nlohmann JSON binary dir: ${nlohmann_json_BINARY_DIR}")

    # we don't really care so much about a third party library's tests to be

    # run from our own project's code

    set(JSON_BuildTests OFF CACHE INTERNAL "")

    # we also don't need to install it when our main project gets installed

    set(JSON_Install OFF CACHE INTERNAL "")

    add_subdirectory(${nlohmann_json_SOURCE_DIR} ${nlohmann_json_BINARY_DIR})

endif()