missing ~amd64 keyword for net-proxy/squidclam. Squidclam compiles correctly.
From package.mask: # Alin Nastac <mrness@gentoo.org> (20 Sep 2006) # Masked due to its proven inability to work with squid-2.6. # Pending for removal on 20 Oct 2006. # Please uninstall it and emerge net-proxy/squidclamav instead.