runtime: Unable to compile HelloWorld.cs on Ubuntu after following instructions

I followed the instructions here but the 2nd-to-last step (mcs) fails with:

glen@ubuntu:~/coreclr-demo/runtime$ mcs /nostdlib /noconfig /r:../packages/System.Console.4.0.0-beta-22512/lib/contract/System.Console.dll /r:../packages/System.Runtime.4.0.20-beta-22512/lib/contract/System.Runtime.dll HelloWorld.cs
error CS0009: Metadata file `/home/glen/coreclr-demo/runtime/../packages/System.Runtime.4.0.20-beta-22512/lib/contract/System.Runtime.dll' does not contain valid metadata
error CS0518: The predefined type `System.Object' is not defined or imported
error CS0518: The predefined type `System.ValueType' is not defined or imported
error CS0518: The predefined type `System.Attribute' is not defined or imported
error CS0518: The predefined type `System.Int32' is not defined or imported
error CS0518: The predefined type `System.UInt32' is not defined or imported
error CS0518: The predefined type `System.Int64' is not defined or imported
error CS0518: The predefined type `System.UInt64' is not defined or imported
error CS0518: The predefined type `System.Single' is not defined or imported
error CS0518: The predefined type `System.Double' is not defined or imported
error CS0518: The predefined type `System.Char' is not defined or imported
error CS0518: The predefined type `System.Int16' is not defined or imported
error CS0518: The predefined type `System.Decimal' is not defined or imported
error CS0518: The predefined type `System.Boolean' is not defined or imported
error CS0518: The predefined type `System.SByte' is not defined or imported
error CS0518: The predefined type `System.Byte' is not defined or imported
error CS0518: The predefined type `System.UInt16' is not defined or imported
error CS0518: The predefined type `System.String' is not defined or imported
error CS0518: The predefined type `System.Enum' is not defined or imported
error CS0518: The predefined type `System.Delegate' is not defined or imported
error CS0518: The predefined type `System.MulticastDelegate' is not defined or imported
error CS0518: The predefined type `System.Void' is not defined or imported
error CS0518: The predefined type `System.Array' is not defined or imported
error CS0518: The predefined type `System.Type' is not defined or imported
error CS0518: The predefined type `System.Collections.IEnumerator' is not defined or imported
error CS0518: The predefined type `System.Collections.IEnumerable' is not defined or imported
error CS0518: The predefined type `System.IDisposable' is not defined or imported
error CS0518: The predefined type `System.IntPtr' is not defined or imported
error CS0518: The predefined type `System.UIntPtr' is not defined or imported
error CS0518: The predefined type `System.RuntimeFieldHandle' is not defined or imported
error CS0518: The predefined type `System.RuntimeTypeHandle' is not defined or imported
error CS0518: The predefined type `System.Exception' is not defined or imported
Compilation failed: 32 error(s), 0 warnings

Distro: Ubuntu 14.04.1 LTS