[SPIRV Backend] Reland 76d83e6250854 once IGC side is fixed

### Describe the bug

https://github.com/intel/llvm/commit/76d83e62508548b5f43baa482f74d24886efb763 is causing massive failures https://github.com/intel/llvm/actions/runs/15034362449/job/42254054871

error: undefined reference to _Z41__spirv_GenericCastToPtrExplicit_ToGlobalPU3AS4li'`. It looks like IGC issue.

76d83e6250854 is reverted temporarily in https://github.com/intel/llvm/pull/18403.

We should follow up to get fix and reland once the fix is in.

### To reproduce

/bin/clang++ -Werror -fsycl -fsycl-targets=spir64 -fsycl-use-spirv-backend-for-spirv-gen -Wno-unused-command-line-argument /sycl/test-e2e/Basic/vector/load_store.cpp -o bad.out
env ONEAPI_DEVICE_SELECTOR=level_zero:gpu ./bad.out

### Environment

- OS: [e.g Windows/Linux]
- Target device and vendor: [e.g. Intel GPU]
- DPC++ version: [e.g. commit hash or output of `clang++ --version`]
- Dependencies version: [e.g. the output of `sycl-ls --verbose`]

### Additional context

_No response_