fix rkcommon exported target information on windows
fix rkcommon exported target information on windows

A dependent project (OSPStudio) was trying to link the
rkcommon*.cmake files and failing to compile. This change
makes the glob more stringent on that platform so that
it only picks up the library files.

ospray/OSPRay,ospray/OSPRay,ospray/OSPRay,wilsonCernWq/ospray,wilsonCernWq/ospray,wilsonCernWq/ospray,ospray/OSPRay