Exclude second Ant JAR from classpath in hdfs builds

I've no evidence that this is a problem, but I have known it to be in different projects:

    [junit] WARNING: multiple versions of ant detected in path for junit 
    [junit]          jar:file:/Users/slo/Java/Apache/ant/lib/ant.jar!/org/apache/tools/ant/Project.class
    [junit]      and jar:file:/Users/slo/.ivy2/cache/ant/ant/jars/ant-1.6.5.jar!/org/apache/tools/ant/Project.class

Somehow Ivy needs to be set up to skip pulling in an old version of Ant in the build -both paranamer-ant and jsp-2.1 declare a dependency on it. If both tools are only ever run under Ant, the ivy.xml file could exclude it, the build file just has to make sure that Ant's own classpath gets passed down.