How do I create a solution-level NuGet package. That is, one that does not touch any projects, and is listed in .nuget\packages.config (not in any project-level packages.config files).
For example, psake and RavenDB.Server are solution-level NuGet packages.
I can't find anything in the docs for .nuspec files or nuget.exe that says anything about solution-level packages. I can't find anything special in the build processes of those two projects when they call nuget pack. In fact, I can't find a single search result at all about creating solution-level packages.