Repro:

1. Create a netcoreapp1.1 default exe project.
2. Add <DisableImplicitFrameworkReferences>true</DisableImplicitFrameworkReferences>
3. Add references (System.Runtime, etc) as necessary to get it to compile.
4. Publish.

The runtimeconfig.json is now empty instead of the expected netcoreapp1.1. There should be some way to manually specify the target runtime framework without referencing the NETCore.App package.