[clang] [llvm] [SPIR-V] Add builtin/intrinsic for subgroup ballot (PR #174862)

[Farzon Lotfi via cfe-commits]

farzonl wrote:

> Updated, now hopefully no one tells me that someone added something for #174655 already too

That one you are reusing an existing intrinsic so it’s different. That pr is just adding clang target extensions. 

https://github.com/llvm/llvm-project/pull/174862