ILMerge does not run in source-build

[crummel]

See #708 (comment), extra files in sdk/<version>/Sdks/NuGet.Build.Tasks.Pack/CoreCLR:

• NuGet.Commands.dll
• NuGet.Common.dll
• NuGet.Configuration.dll
• NuGet.Credentials.dll
• NuGet.DependencyResolver.Core.dll
• NuGet.Frameworks.dll
• NuGet.LibraryModel.dll
• NuGet.Packaging.Core.dll
• NuGet.Packaging.dll
• NuGet.ProjectModel.dll
• NuGet.Protocol.dll
• NuGet.Versioning.dll

Note that the sibling Desktop folder is of interest since we now build net46 assets for NuGet but probably not strictly required.

[crummel]

This is because NuGet ILMerges their build output in the official build, where we do not (because ILMerge only runs on Windows). We should still have identical functionality, just in multiple files.

[omajid]

Can we leave this open to track the issue? If the ultimate goal of source-build is to end up as a possible replacement/substitute of the prodcon build, then issues like these will need to be addressed (somehow). Otherwise source-build will remain a second class citizen.

[crummel]

Sure, reopened. I'll rename to clarify too.

[dagood]

Related PR for future reference: NuGet/NuGet.Client#2560. It's a maintenance fix for the workaround we're using to get all the NuGet DLLs we need even though we can't ILMerge.