"emerge frostwire" worked up to this point:
* Detected file collision(s):
* Searching all installed packages for file collisions...
* Press Ctrl-C to Stop
* None of the installed packages claim the file(s).
* Package 'dev-java/ant-core-1.7.1-r4' NOT merged due to file
* collisions. If necessary, refer to your elog messages for the whole
* content of the above message.
>>> Failed to install dev-java/ant-core-1.7.1-r4, Log file:
I removed the file bin from /usr/share/ant; it was a broken symlink to /usr/share/ant-core. Then it installed fine.