The package clipper2 can be imported via CMake FindPkgConfig module:

    # Clipper2
    find_package(PkgConfig REQUIRED)
    pkg_check_modules(Clipper2 REQUIRED IMPORTED_TARGET Clipper2)
    target_link_libraries(main PkgConfig::Clipper2)

    # Clipper2Z
    find_package(PkgConfig REQUIRED)
    pkg_check_modules(Clipper2Z REQUIRED IMPORTED_TARGET Clipper2Z)
    target_link_libraries(main PkgConfig::Clipper2Z)

clipper2 provides CMake targets:

    # Clipper2
    find_package(Clipper2 CONFIG REQUIRED)
    target_link_libraries(main PRIVATE Clipper2::Clipper2)

    # Clipper2Z
    find_package(Clipper2 CONFIG REQUIRED)
    target_link_libraries(main PRIVATE Clipper2::Clipper2Z)