[UR] Use reference counting on factories

Pre-commit MR for oneapi-src/unified-runtime#2048

Author: RossBrunton

sycl/cmake/modules/FetchUnifiedRuntime.cmake

@@ -116,14 +116,12 @@ if(SYCL_UR_USE_FETCH_CONTENT)
       CACHE PATH "Path to external '${name}' adapter source dir" FORCE)
   endfunction()
 
-  set(UNIFIED_RUNTIME_REPO "https://github.com/oneapi-src/unified-runtime.git")
-  # commit 8c9dd7e464a99ebbfb238ac2dabefc3ac77baea5
-  # Merge: a99dbcee 3abe18cf
-  # Author: Piotr Balcer <piotr.balcer@intel.com>
-  # Date:   Fri Sep 6 17:21:17 2024 +0200
-  #   Merge pull request #1820 from pbalcer/static-linking
-  #   Add support for static linking of the L0 adapter
-  set(UNIFIED_RUNTIME_TAG 8c9dd7e464a99ebbfb238ac2dabefc3ac77baea5)
+  set(UNIFIED_RUNTIME_REPO "https://github.com/RossBrunton/unified-runtime.git")
+  # commit put-commit-here
+  # Author: Ross Brunton <ross@codeplay.com>
+  # Date:   Wed Sep 4 17:25:11 2024 +0100
+  # Use reference counting on factories
+  set(UNIFIED_RUNTIME_TAG 3a6ed49bd4d988618de1a30a7f461c6414f52b6b)
 
   set(UMF_BUILD_EXAMPLES OFF CACHE INTERNAL "EXAMPLES")
   # Due to the use of dependentloadflag and no installer for UMF and hwloc we need