cmake HAS_FUZZER examples

mchalupa/dg CMakeLists.txt :162 

check_cxx_source_compiles(
   "#include <cstddef>
    extern \"C\" int LLVMFuzzerTestOneInput(const void *, size_t) { return 0; }"
    HAS_FUZZER)

mchalupa/dg CMakeLists.txt :168 

option(ENABLE_FUZZING "Enable fuzzing tests" ${HAS_FUZZER})