Imports System.Core
It is not clear why that's in your source code, you don't need it. But yes, that's going to generate an error since none of the assemblies you added to params.ReferencedAssemblies has that namespace. You'd also have to add System.Core.dll. Same for System.Data, that requires a reference to System.Data.dll. Etcetera.
Look in your own project for the list of standard framework assembly references. Project + Properties, References tab.
I should note that this mishap is odd. Unless the compiler is called with the /noconfig option, it should be automatically using the vbc.rsp file which already adds references for all the common framework assemblies. I don't readily see a reason why that's not happening in your case.