[clang] [clang][HLSL] Update DXIL/SPIRV hybird CodeGen tests to use temp var (PR #105930)

[Amr Hesham via cfe-commits]

AmrDeveloper wrote:

> Looks great, thanks! Do you need someone to commit this for you?

Yes please, i don't have commit access yet :D

https://github.com/llvm/llvm-project/pull/105930