[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

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Co-authored-by: Joseph Huber <huberjn@outlook.com>
GitOrigin-RevId: 8db9774118ccdfc583ed230cbdde1c56567d0643
8 files changed