Fatal error in Mono IL Linker Mono.Cecil.ResolutionException: Failed to resolve

MonoLinker.exe crashes instead of giving a useful error when Cecil can't resolve a type or member

There can be multiple assemblies and situation with these symptoms, I'm adding one concrete repro as an example. Here, a Blazor WASM project is referencing a NuGet package, `Microsoft.Build` version `16.6.0`. The WASM project is targeting `netstandard2.1`, however the Microsoft.Build.dll is targeting either `net472` or `netcoreapp2.1`. During the build of the Blazor project there's an MSBuild warning:

```
C:\MSBuildStructuredLog\Blazor App\StructuredLogViewerWASM.csproj warning NU1701: Package 'Microsoft.Build 16.6.0' was restored using '.NETFramework,Version=v4.6.1, .NETFramework,Version=v4.6.2, .NETFramework,Version=v4.7, .NETFramework,Version=v4.7.1, .NETFramework,Version=v4.7.2, .NETFramework,Version=v4.8' instead of the project target framework '.NETStandard,Version=v2.1'. This package may not be fully compatible with your project. [C:\MSBuildStructuredLog\Blazor App\StructuredLogViewerWASM.csproj]
```

The symptoms I get later when calling monolinker.exe:

```
Fatal error in Mono IL Linker
C:\Users\kiril\.nuget\packages\microsoft.aspnetcore.components.webassembly.buil
d\3.2.1\targets\Blazor.MonoRuntime.targets(326,5): error : Unhandled exception.
Mono.Cecil.ResolutionException: Failed to resolve System.Runtime.Remoting.Life
time.ClientSponsor [C:\MSBuildStructuredLog\Blazor App\StructuredLogViewerWASM.
csproj]
at Mono.Linker.Steps.MarkStep.HandleUnresolvedType(TypeReference reference
)
at Mono.Linker.Steps.MarkStep.MarkType(TypeReference reference)
at Mono.Linker.Steps.MarkStep.MarkField(FieldDefinition field)
at Mono.Linker.Steps.MarkStep.MarkEntireType(TypeDefinition type)
at Mono.Linker.Steps.MarkStep.MarkEntireAssembly(AssemblyDefinition assemb
ly)
at Mono.Linker.Steps.MarkStep.InitializeAssembly(AssemblyDefinition assemb
ly)
at Mono.Linker.Steps.MarkStep.Initialize()
at Mono.Linker.Steps.MarkStep.Process(LinkContext context)
at Mono.Linker.Pipeline.ProcessStep(LinkContext context, IStep step)
at Mono.Linker.Pipeline.Process(LinkContext context)
at Mono.Linker.Driver.Run(ILogger customLogger)
at Mono.Linker.Driver.Execute(String[] args, ILogger customLogger)
at Mono.Linker.Driver.Main(String[] args)
C:\Users\kiril\.nuget\packages\microsoft.aspnetcore.components.webassembly.buil
d\3.2.1\targets\Blazor.MonoRuntime.targets(326,5): error : ILLink failed with e
xit code -532462766. [C:\MSBuildStructuredLog\Blazor App\StructuredLogViewerWAS
M.csproj]
```

Repro steps (on Windows):
1. git clone https://github.com/KirillOsenkov/MSBuildStructuredLog
2. git checkout monolinkerbug (or use SHA 1e3dd0be3f21fc9a222f19ee5871aec8aaf587ab)
3. cd "MSBuildStructuredLog\Blazor App"
4. msbuild /r /bl /p:DeployOnBuild=true;PublishProfile=FolderProfile

You may need to publish the Blazor App project to a Folder first using Visual Studio to create a publish profile.

Or you can run the monolinker directly and use this info:
1. C:\Users\kiril\.nuget\packages\microsoft.aspnetcore.components.webassembly.runtime\3.2.0\tools\monolinker\monolinker.exe
2. .rsp file: https://gist.github.com/KirillOsenkov/4be472ddcd219b75b09d3d35995b298f
3. pass the .rsp file as an argument to monolinker.exe: `"@C:\MSBuildStructuredLog\Blazor App\linker.rsp"`

Basically when failing to resolve types or members at the stack above it shouldn't crash but should log the assembly which contained a reference that could not be resolved. Usually given the full path to the problematic assembly it'll be easier to reason what is wrong.

In our case the problematic assembly was `C:\Users\kiril\.nuget\packages\microsoft.build\16.6.0\lib\net472\Microsoft.Build.dll` and it was easier to see that it doesn't target netstandard2.1 and it would cause problems.