Ensure that the dependency checking will check the time of the target file rather than the containing directory

git-svn-id: https://svn.apache.org/repos/asf/buildr/trunk@1537851 13f79535-47bb-0310-9956-ffa450edef68
Move the clobber task outside the catch block and add a few directories to the list removed

git-svn-id: https://svn.apache.org/repos/asf/buildr/trunk@1537852 13f79535-47bb-0310-9956-ffa450edef68