ref assembly generation is wrong when inheriting from manually implemented class

See example here: https://github.com/aspnet/AspNetCore/pull/8811#discussion_r269242361

Moving a type to have it's ref assembly type generated manually caused it to be omitted from the inheritance hierarchy of other types.

Ex:
```
class ComponentBase { }
class InputBase : ComponentBase { }
class InputText : InputBase { }
```

Moving `InputBase` to be manual caused the declaration for `InputText` to be generated as `class InputBase : ComponentBase { }`