The package gmp can be imported via CMake FindPkgConfig module:

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

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