Unified configuration/building system for ARC V1 and V2 

Unified configuration/building system for either architectural variants. Now, selecting --with-multilib, the building infrastructure builds the required libraries for EM or ARC600/ARC700. I.e., selecting with-cpu=arc700, the multilib feature builds additionally EM specific libs. While with-cpu=EM, the multilib feature builds ARCv1 specific libs.