Remove some warnings in tests

include/boost/static_string/config.hpp

@@ -62,11 +62,13 @@
 
 // Can we use [[nodiscard]]?
 // KRYSTIAN TODO: these checks need to be improved
-#if defined(__has_attribute) && __has_attribute(nodiscard)
+#if defined(__has_attribute)
+#if __has_attribute(nodiscard)
 #define BOOST_STATIC_STRING_NODISCARD [[nodiscard]]
 #else
 #define BOOST_STATIC_STRING_NODISCARD
 #endif
+#endif
 
 // _MSVC_LANG isn't avaliable until after VS2015
 #if defined(_MSC_VER) && _MSC_VER < 1910L