Referencing v1 Functions SDK blocks NuGet package auto-gen

Short version: if the v1 Functions SDK is referenced, VS will not auto-gen a NuGet package (I realize this is an unusual scenario...)

I started with a v1 Functions app, which means it targets `net461` but uses the newer SDK-format csproj file. Of course, Functions apps are really just class libraries under the hood. The project was used to build dependency injection capabilities which I wanted to package as a reusable library, so the end result didn't include any triggers, just classes for attributes and various WebJobs extensions.

However, when I turned on the Generate option on the Package property page, no packages are created when I build.

After some trial and error, it turns out this only happens when I reference `Microsoft.NET.Sdk.Functions` (currently v1.0.7). I created a new .NET Standard class library, edited the csproj to target `net461`, then referenced the individual packages that the SDK uses, added in all my classes again, and that _does_ also generate a NuGet package.

I'm guessing this is intentional (a normal Functions project would have no need for package output), but I figured I'd report it in case it's some sort of bug.