Fix building with newer glibc #512106 by Paweł Hajdan, Jr..

(Portage version: 2.2.10/cvs/Linux x86_64, signed Manifest commit with key D2E96200)
Install cups-config for all ABIs, and add it to MULTILIB_CHOST_TOOLS.

(Portage version: 2.2.10/cvs/Linux x86_64, signed Manifest commit with key EFB4464E!)