Separate into std_async test

Author: Dobiasd

test/show_versions.cpp

@@ -33,6 +33,10 @@ TEST_CASE("show_versions - print_defines")
     std::cout << "__GLIBCXX__: " << __GLIBCXX__ << std::endl;
 #endif
 
+}
+
+TEST_CASE("show_versions - std_async")
+{
     auto handle = std::async(std::launch::async, []() { return 1; });
     auto result = handle.get();
 }