[clang] [SYCL][Driver] Emit textual SPIR-V for device-only -S compilations (PR #227844)

[Alexey Bader via cfe-commits]

bader wrote:

> @bader, does this change raise any concerns for you?

I don't have concerns regarding this specific change.

But in general, there should be no checks in this place. Backend phase handles offload languages uniformly already.
Driver can set `-emit-llvm` for SYCL (which current condition emulates) to remove the need for SYCL specific checks and in the long-run add support for LTO mode.

https://github.com/llvm/llvm-project/pull/227844