Fix issue with drive letter under windows

The get_filename_component gets stuck under windows when finding the
parent directory for a drive letter. This basically reverts to using the
full path, which is more likely to be ok under windows

Signed-off-by: Kimball Thurston <kdt3rd@gmail.com>

PyIlmBase/CMakeLists.txt

@@ -63,7 +63,9 @@ function(PYILMBASE_EXTRACT_REL_SITEARCH varname pyver pyexe pysitearch)
     get_filename_component(_nexedir ${_exedir} DIRECTORY)
     string(FIND ${pysitearch} ${_nexedir} _findloc)
     if (_nexedir STREQUAL _exedir)
-        message(FATAL_ERROR "Unable to get parent directory for ${_exedir}")
+        message(WARNING "Unable to get parent directory for ${_exedir}, using absolute python site arch folder ${pysitearch}")
+        set(_elen -1)
+        break()
     else()
         set(_exedir ${_nexedir})
     endif()