Update aspnetcore-base-runtime.proj

Author: jkoritzinsky

src/Framework/App.Runtime/src/aspnetcore-base-runtime.proj

@@ -8,6 +8,7 @@
       This version file is required by source-build.
     -->
     <ExcludeFromSourceOnlyBuild>false</ExcludeFromSourceOnlyBuild>
+    <IsPackable>false</IsPackable>
   </PropertyGroup>
 
   <Target Name="WriteBaseRuntimeVersionFile" AfterTargets="Build">