[Driver][SYCL] Allow native_cpu and CUDA-compat triples in SYCL device compilation (#22174)
Commit 32ab88d2bac6 added a check in CompilerInstance::createTarget()
that rejects -fsycl-is-device with any non-GPU triple. There are two
legitimate cases in intel/llv sycl branch not covered by isGPU():
- native_cpu
- SYCL CUDA compat mode (-fsycl-cuda-compatibility): uses x86_64 as the
compilation triple with -fsycl-is-device to run SYCL diagnostics over
CUDA-annotated code.
Extend the check to also allow isNativeCPU() and SYCLCUDACompat.
Update tests that were using x86_64 with -fsycl-is-device without either
of these two justifications.
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>