cmake DEAL_II_HAVE_BUILTIN_EXPECT examples

dealii/dealii cmake/checks/check_02_compiler_features.cmake :113 

CHECK_CXX_SOURCE_COMPILES(
    "
    bool f() { return true; }
    int main(){ if (__builtin_expect(f(),false)) {} }
    "
    DEAL_II_HAVE_BUILTIN_EXPECT)