[llvm] [SPIR-V] Improve portability of the code (PR #123584)

[Michal Paszkowski via llvm-commits]

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

@VyacheslavLevytskyy You were quicker :) I was just about to push nearly exactly the same changes. 

https://github.com/llvm/llvm-project/pull/123584