COMP: Ensure Slicer_RemoteModule_Add worked when source directory is passed

Configuring Slicer with -D<projectname>_SOURCE_DIR:PATH=/path/to/projectname
is now supported.

Thanks to Bradley Lowekamp <blowekamp@mail.nih.gov> for reporting the issue.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22806 3bd1e089-480b-0410-8dfb-8563597acbee