[clang] [NFC][clang] Fix CodeGenSYCL::unique_stable_name_windows_diff test (PR #146854)

[Mariya Podchishchaeva via cfe-commits]

Fznamznon wrote:

I noticed there is a problem with __builtin_sycl_unique_stable_name and sycl_kernel_etnry_point attribute. If I add this wrapping of __builtin_sycl_unique_stable_name calls AND sycl_kernel_entry_point attribute, the strings disappear from the IR. They are in here https://godbolt.org/z/KnPffTMYq , they disappear in https://godbolt.org/z/6jdvYEhK7 . Makes sense to fix it first instead of merging this.

https://github.com/llvm/llvm-project/pull/146854