Merging sys-apps/coreutils-5.2.1-r7 is blocked 'coz it wants to overwrite /bin/hostid. equery b /bin/hostid says it does not belong to any package. After rm /bin/hostid && emerge coreutils equery b /bin/hostid reports the correctly sys-apps/coreutils-5.2.1-r7 (/bin/hostid)
Well, we can't fix collisions with orphaned files. Reopen if you find out what installed /bin/hostid on your system.