Fix the determination of the base directory to handle an explicitly supplied base_dir
Fix the determination of the base directory to handle an explicitly supplied base_dir

git-svn-id: d8f3215415546ce936cf3b822120ca56e5ebeaa0@1443291 13f79535-47bb-0310-9956-ffa450edef68

apache/buildr,liamchristopher/buildr,stewi2/buildr,mariusk/buildr-kawa,jpcaruana/buildr,jpcaruana/buildr,liamchristopher/buildr,mariusk/buildr-kawa,mariusk/buildr-kawa,jpcaruana/buildr,stewi2/buildr,liamchristopher/buildr,apache/buildr,apache/buildr,stewi2/buildr,stewi2/buildr,apache/buildr,liamchristopher/buildr,jpcaruana/buildr