COMP: Fix config error introduced in r21943 by using PYTHON_LIBRARY_PATH

See issue #1180 - http://www.na-mic.org/Bug/view.php?id=1180

git-svn-id: http://svn.slicer.org/Slicer4/trunk@21948 3bd1e089-480b-0410-8dfb-8563597acbee