tomcat etc # emerge -pv ant-contrib

These are the packages that I would merge, in order:

Calculating dependencies
!!! All ebuilds that could satisfy "ant-contrib" have been masked.
!!! One of the following masked packages is required to complete your request:
- dev-java/ant-contrib-1.0_beta2 (masked by: ~amd64 keyword)

For more information, see MASKED PACKAGES section in the emerge man page or
refer to the Gentoo Handbook.