COMP: Fix installation of DCMTK apps on windows

Following commit r21849, DCMTK is used from the build tree and it is required
to specify the intermediate directory. Since package are made only in Release,
the value is forced to Release.

Ideally, dcmtk apps and library should be installed using DCMTK install
system by setting CPACK_INSTALL_CMAKE_PROJECTS.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@21855 3bd1e089-480b-0410-8dfb-8563597acbee