cmake DEAL_II_COMPILER_HAS_FUSE_LD_MOLD examples

dealii/dealii cmake/checks/check_02_compiler_features.cmake :374 

CHECK_CXX_SOURCE_COMPILES(
    "
    #include <iostream>
    void foo() { std::cout << \"Hello, world!\" << std::endl; }
    "
    DEAL_II_COMPILER_HAS_FUSE_LD_MOLD)