roslyn: Can't debug source generator using roslyn component if total dependency file path lengths is too big

Here is a repo with steps to reproduce the problem: https://github.com/KieranDevvs/SourceGeneratorBugSample/tree/master I also encounter this when referencing non nuget packages i.e David Fowlers Bedrock.Framework package. (I can’t confirm this as it is the only package that I have used that is not in a nuget.org feed thus the problem may be related to something else).

This is using the 5.0.400 SDK in VS2019 version 16.11.1 (also described within the repo readme).

Steps to reproduce:

1. Install the .NET compiler platform SDK (described in this post: http://stevetalkscode.co.uk/debug-source-generators-with-vs2019-1610)
2. Clone the repository and open it in visual studio 2019 version 16.11.1.
3. Build the solution and find no build errors.
4. Set the SourceGenerator project to be the startup project.
5. Debug the project.
6. See error:

1. Open the SomeLibrary csproj file and remove <FrameworkReference Include="Microsoft.AspNetCore.App" />.
2. Debug the project again, this time no error will show and the project will successfully execute with the debugger attached.

This also appears to occour with dependencies that arent in nuget.org (I cant confirm this easily as I have only used one dependency that did not come from nuget.org thus, this may just be a coincidence).