Correct condition for copying openthreads PDB
Correct condition for copying openthreads PDB

Related to issue: https://github.com/openscenegraph/OpenSceneGraph/issues/898
openscenegraph/osg,openscenegraph/osg,scrawl/osg,openscenegraph/osg,scrawl/osg,openscenegraph/osg,scrawl/osg,scrawl/osg