Description
For targeting packs, the SDK first checks if they are in the dotnet packs folder. If they are it uses them from there, otherwise it generates a PackageDownload item so that they will be downloaded to the packages folder as part of NuGet restore.
Currently, we don't check for runtime packs in the packs folder. This is because we haven't shipped any with the .NET SDK, as they are only used for self-contained apps and there are many different runtime packs for different RuntimeIdentifiers which represent different OS/architecture combinations.
For .NET 6, iOS and Android apps will need runtime packs, and the set of target RuntimeIdentifiers will be more limited. So they would like to deliver runtime packs as part of their optional SDK workloads.
This means we should update the SDK runtime pack resolution logic to first look in the dotnet packs folder and resolve from there if possible, before generating a PackageDownload item to download the runtime pack if necessary.