Created attachment 349836 [details] build.log This is happening on a new system, trying to emerge icedtea-7.2.3.9 as its first jdk via gcj-jdk.
It seems to me that (some part of) ant would need to go into DEPEND as disabling the check is no option.
`emerge -1v ant-core` was sufficient, now it builds.
Fixed, thanks for the report.