[clang] [llvm] [SPIRV] Add Target Builtins using Distance ext as an example (PR #121598)

[Vlad Serebrennikov via llvm-commits]

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

Yes, you handled the creation of `SemaSPIRV` perfectly.
(I'm the one who introduced the rest of `Sema*` parts.)

https://github.com/llvm/llvm-project/pull/121598