COMP: LibArchive-* dirs should be deleted to avoid build errors

Forcing "HAVE_LIBXML_XMLREADER_H" to a "notfound" value as it is
done in commit r22012 has no effect on an existing build tree.

This is confirmed by http://slicer.cdash.org/viewBuildError.php?buildid=98584

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22013 3bd1e089-480b-0410-8dfb-8563597acbee