WMC9999 errors do not tell you which XAML file is at fault #10510
Description
Describe the bug
When a WMC9999 error occurs, it points to the XAML compiler .targets file instead of the problematic XAML file, making it practically impossible to debug in a large project. Example of such an error:
Error (active) WMC9999 Data at the root level is invalid. Line 1, position 2. ProjectName (net8.0-windows10.0.26100) C:\Users\UserName\.nuget\packages\microsoft.windowsappsdk\1.6.250228001\buildTransitive\Microsoft.UI.Xaml.Markup.Compiler.interop.targets 505
Steps to reproduce the bug
Compile a project that contains a XAML file with invalid content that triggers WMC9999 and observe the error above.
Expected behavior
The error should report similar to how it does on Uno Platform targets where it points to the offending XAML file and makes finding the problem much easier:
Error (active) UXAML0001 Data at the root level is invalid. Line 1, position 2. ProjectName (net8.0-android), ProjectName (net8.0-browserwasm), ProjectName (net8.0-desktop), ProjectName (net8.0-ios), ProjectName (net8.0-maccatalyst) C:\repos\ProjectName\ProjectName\Presentation\InterpreterSelectionDialog.xaml 1
Screenshots
No response
NuGet package version
None
Windows version
No response
Additional context
No response