[SYCL][Reduction] Fix race condition in withAuxHandler (#7563)

Author: aelovikov-intel

sycl/include/sycl/reduction.hpp

@@ -821,8 +821,9 @@ auto make_reduction(RedOutVar RedVar, RestTy &&...Rest) {
 namespace reduction {
 inline void finalizeHandler(handler &CGH) { CGH.finalize(); }
 template <class FunctorTy> void withAuxHandler(handler &CGH, FunctorTy Func) {
-  CGH.finalize();
+  event E = CGH.finalize();
   handler AuxHandler(CGH.MQueue, CGH.MIsHost);
+  AuxHandler.depends_on(E);
   AuxHandler.saveCodeLoc(CGH.MCodeLoc);
   Func(AuxHandler);
   CGH.MLastEvent = AuxHandler.finalize();