Improve make_classpath_mvn to take advantage of mvn and the dependency:build-classpath goal where possible instead of relying on the .classpath file search approach which can fail horribly depending on what is in the .classpath file (certainly it fails horribly on OS X)

git-svn-id: https://svn.apache.org/repos/asf/jena/trunk@1576775 13f79535-47bb-0310-9956-ffa450edef68