NativeAOT IL9702 false positives when publishing shared libraries

[jpovixwm]

Hello.
Ever since #605 was merged, publishing any shared libraries appears to generate the IL9702 warning.
The issue can be easily reproduced with the NativeLibrary sample:

$ dotnet publish -p:NativeLib=Shared -p:SelfContained=true -r win-x64 -c release
Microsoft (R) Build Engine version 16.8.3+39993bd9d for .NET
Copyright (C) Microsoft Corporation. All rights reserved.

  Determining projects to restore...
  Restored C:\runtimelab\samples\NativeLibrary\NativeLibrary.csproj (in 949 ms).
  NativeLibrary -> C:\runtimelab\samples\NativeLibrary\bin\release\net5.0\win-x64\NativeLibrary.dll
  Generating compatible native code. To optimize for size or speed, visit https://aka.ms/OptimizeCoreRT
/_/src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/EventSource.cs(1699): AOT analysis warning IL9702: System.Diagnostics.Tracing.EventSource.DecodeObject(Int32,Int32,EventData*&): Marshal.SizeOf was called with an unknown type. It might not be possible to compute the marshalling size at runtime. [C:\runtimelab\samples\NativeLibrary\NativeLibrary.csproj]
     Creating library bin\release\net5.0\win-x64\native\NativeLibrary.lib and object bin\release\net5.0\win-x64\native\NativeLibrary.exp
  NativeLibrary -> C:\runtimelab\samples\NativeLibrary\bin\release\net5.0\win-x64\publish\

The warning is generated even when all of the code in Class1.cs is commented out.

[MichalStrehovsky]

This will be gone once this branch ingests dotnet/runtime#47521. You can ignore this. The warning indicates a potential problem, but not really because the types are always blittable.