Sync from upstream.

test/Jamfile.v2

@@ -229,6 +229,7 @@ run empty_value_test.cpp ;
 run empty_value_size_test.cpp ;
 run empty_value_final_test.cpp ;
 run empty_value_constexpr_test.cpp ;
+compile empty_value_nested_test.cpp ;
 compile-fail empty_value_compile_fail_casting.cpp ;
 
 run quick_exit_test.cpp ;