CMake: vrpn (and its igate module) require -fexceptions

Per #development comment by rdb earlier today

panda/CMakeLists.txt

@@ -139,6 +139,7 @@ if(INTERROGATE_PYTHON_INTERFACE)
 
   if(HAVE_VRPN)
     add_python_module(panda3d.vrpn p3vrpn IMPORT panda3d.core COMPONENT VRPNPython)
+    set_target_properties(panda3d.vrpn PROPERTIES CXX_EXCEPTIONS ON)
 
     export_targets(VRPNPython NAMESPACE "Panda3D::Python::" COMPONENT VRPNDevel)
   endif()

panda/src/vrpn/CMakeLists.txt

@@ -35,6 +35,8 @@ set_target_properties(p3vrpn PROPERTIES DEFINE_SYMBOL BUILDING_VRPN)
 target_link_libraries(p3vrpn panda PKG::VRPN)
 target_interrogate(p3vrpn ALL)
 
+set_target_properties(p3vrpn PROPERTIES CXX_EXCEPTIONS ON)
+
 install(TARGETS p3vrpn
   EXPORT VRPN COMPONENT VRPN
   DESTINATION ${CMAKE_INSTALL_LIBDIR}