COMP: Fix python build error occurring when using VisualStudio with Ninja

This has been tested on Visual Studio 2008, 2012, and 2012+Ninja

See https://github.com/davidsansome/python-cmake-buildsystem/pull/23

From: Isaiah Norton <inorton@bwh.harvard.edu>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22154 3bd1e089-480b-0410-8dfb-8563597acbee