message: oh come on! clang builds - warnings...
diff: @@ -9,8 +9,8 @@ DOCTEST_MAKE_STD_HEADERS_CLEAN_FROM_WARNINGS_ON_WALL_BEGIN
  #include <stdexcept>
  DOCTEST_MAKE_STD_HEADERS_CLEAN_FROM_WARNINGS_ON_WALL_END
  -std::exception_ptr g_exception_ptr = nullptr;
  -std::mutex g_mutex;
  +static std::exception_ptr g_exception_ptr = nullptr;
  +static std::mutex g_mutex;
  TEST_CASE("threads...") {
  auto call_from_thread = [](int value) {
  