cmake OPENMP_HAVE_ONEAPI_COMPILER examples

Lewuathe/mlir-hello thirdparty/llvm-project/openmp/cmake/config-ix.cmake :6

check_cxx_source_compiles("#if (defined(__INTEL_CLANG_COMPILER) || defined(__INTEL_LLVM_COMPILER))
                             int main() { return 0; }
                             #else
                             not oneAPI
                             #endif" OPENMP_HAVE_ONEAPI_COMPILER)