make sure target directory is in finder classpath for cleaning as well as weaving; abort with a warning if target directory does not exist

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/weaver/trunk@1568046 13f79535-47bb-0310-9956-ffa450edef68
add cleaning for Antlib test

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/weaver/trunk@1568047 13f79535-47bb-0310-9956-ffa450edef68