[GeneratedComInterface] Produces SYSLIB1051 in WinUI3 project even though I have DisableRuntimeMarshalling=true

### Description

In a WinUI3 project I get errors telling me that I need to set DisableRuntimeMarshalling but I have done so. And if I add `[assembly:DisableRuntimeMarshalling]` then I get a "duplicate attribute defined" later during compile.

### Reproduction Steps

I pushed a repro up here: https://github.com/jevansaks/WinUI3ComGeneratorsRepro

But the repro is:
1. File => New Project "WinUI Blank App (Packaged)"
2. Add this to the csproj:
```xml
true
true
true
```
3. Add this to app.xaml.cs:
```c#
[Guid("00000000-0000-0000-0000-000000000003"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown), GeneratedComInterface]
public partial interface IRepro
{
void Test(global::System.Drawing.Point pt);
}
```

### Expected behavior

Compiles.

### Actual behavior

Gives a confusing error:
>App.xaml.cs(33,48,33,50): error SYSLIB1051: Runtime marshalling must be disabled in this project by applying the 'System.Runtime.CompilerServices.DisableRuntimeMarshallingAttribute' to the assembly to enable marshalling this type. The generated source will not handle marshalling of parameter 'pt'. (https://learn.microsoft.com/dotnet/fundamentals/syslib-diagnostics/syslib1051)

### Regression?

_No response_

### Known Workarounds

_No response_

### Configuration

_No response_

### Other information

This seems to be because XamlPreCompile doesn't get all the things passed to it that CoreCompile does. Again. Why does this target exist? :)