Can't use unique_ptr because of deleter.

Author: Alexandr-Konovalov

sycl/include/sycl/handler.hpp

@@ -3423,7 +3423,7 @@ class __SYCL_EXPORT handler {
       uint64_t SignalValue);
 
 private:
-  std::unique_ptr<detail::handler_impl> MImplOwner;
+  std::shared_ptr<detail::handler_impl> MImplOwner;
   detail::handler_impl *impl;
   std::shared_ptr<detail::queue_impl> &MQueue;
   std::vector<detail::LocalAccessorImplPtr> MLocalAccStorage;

sycl/source/handler.cpp

@@ -304,7 +304,7 @@ fill_copy_args(detail::handler_impl *impl,
 
 handler::handler(std::shared_ptr<detail::queue_impl> &Queue,
                  bool CallerNeedsEvent)
-    : MImplOwner(std::make_unique<detail::handler_impl>(Queue.get(), nullptr,
+    : MImplOwner(std::make_shared<detail::handler_impl>(Queue.get(), nullptr,
                                                         CallerNeedsEvent)),
       impl(MImplOwner.get()), MQueue(Queue) {}