Reference assembly without csc.rsp file

Is it possible to add a custom assembly to the compilation pipeline without the use of csc.rsp file.
I need that such a an assembly show up in the list of CompilationPipeline.GetAssemblies() because it will be used by another package (not mine) and post process those assemblies.
Using the csc.rsp file won’t make the libraries available in that list anyway.

Thanks

Did you ever find a way?