>>> Compiling source in /var/tmp/portage/dev-java/ant-nodeps-1.7.0/work/apache-ant-1.7.0 ...
 * Using all available ANT_TASKS
Buildfile: build.xml

check_for_optional_packages:

BUILD FAILED
/var/tmp/portage/dev-java/ant-nodeps-1.7.0/work/apache-ant-1.7.0/build.xml:470: java.lang.UnsupportedClassVersionError: junit/framework/TestCase (Unsupported major.minor version 49.0)

Total time: 0 seconds

!!! ERROR: dev-java/ant-nodeps-1.7.0 failed.
Call stack:
  ebuild.sh, line 1611:   Called dyn_compile
  ebuild.sh, line 968:   Called qa_call 'src_compile'
  environment, line 4374:   Called src_compile
  ant-nodeps-1.7.0.ebuild, line 16:   Called eant 'jar-nodeps'
  java-utils-2.eclass, line 1614:   Called die

!!! eant failed
!!! If you need support, post the topmost build error, and the call stack if relevant.
!!! A complete build log is located at '/var/tmp/portage/dev-java/ant-nodeps-1.7.0/temp/build.log'.

!!! When you file a bug report, please include the following information:
GENTOO_VM=blackdown-jdk-1.4.2  CLASSPATH="" JAVA_HOME="/opt/blackdown-jdk-1.4.2.03"
JAVACFLAGS="-source 1.4 -target 1.4" COMPILER="javac"
and of course, the output of emerge --info