Fix dependency context builder regression

[pakrym]

Fix regression in dependency builder when having multiple dependencies with same name.
@anurse

[analogrelay]

when builds succeed

[pranavkm]

Any idea where the IDictionary<>.Add call is? Could we change that to indexer assignment so it doesn't throw?

[pakrym]

I wasn't dictionary add call it's Can not add property System.Collections to Newtonsoft.Json.Linq.JObject. Property with the same name already exists on object. thrown at https://github.com/dotnet/cli/blob/pakrym/deps-duplication-fix/src/Microsoft.Extensions.DependencyModel/DependencyContextWriter.cs#L246

[troydai]

[pranavkm]

[davidfowl]

When does this happen?

[pakrym]

Won't merge per @davidfowl request, we'll need to fix root cause