WinUI class library output path does not consider RuntimeIdentifiers witch publish function expects

### Describe the bug

If you try to publish a WinUI project with a reference to a WinUI call library, the tooling will not find the class library dll because it expects an output path of the library that contains the RuntimeIdentifier.

### Steps to reproduce the bug

1. Create a WinUI project.
2. Create a WinUI class library project.
3. Add a reference to the class library.
4. Try Publish e.g. win-x64 by using Publish menu in context menu of the WinUI project.

Start by reproducing the WinUI publish flow with a referenced WinUI class library and the win-x64 RuntimeIdentifier. Inspect how the tooling resolves the class library output path; done when publishing locates the class library DLL in the RuntimeIdentifier-specific output directory.

Written by the indexing model from the issue text.