In addition to this, you should be getting warnings similar to:
All projects referencing ClassLibrary1.csproj must install nuget package Microsoft.Bcl.Build. For more information, see http://go.microsoft.com/fwlink/?LinkID=317569.
This is indicating a problem. Basically, the short of it, you should be installing HttpClient.Compression into all projects. MSBuild/AppX packaging doesn't know which binary to deploy between the portable library and store library project (they have different APIs & versions). Installing the package into the application, tells it.