[clang] [llvm] [clang] [sycl] Set default device and host triples for SYCL device compilation (PR #172366)

[Tom Honermann via cfe-commits]

https://github.com/tahonermann approved this pull request.

This looks great to me! Thanks @elizabethandrews!

https://github.com/llvm/llvm-project/pull/172366