[OFFLOAD] Build DeviceRTL with SPIRV backend (#174675) This PR adds configuration to build DeviceRTL with SPIRV backend. It is primarily used for level-zero plugin for Intel GPUs --------- Co-authored-by: Joseph Huber <huberjn@outlook.com> GitOrigin-RevId: 8db9774118ccdfc583ed230cbdde1c56567d0643