[Offload] Change ELF machine type for SPIR-V OpenMP image (#159623)
This needs to match the runtime plugin (currently in PR
[here](https://github.com/llvm/llvm-project/pull/158900)), and use the
recently-added `INTELGT` machine type which is correct for Intel GPU
images.
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Signed-off-by: Sarnie, Nick <nick.sarnie@intel.com>