[clang] [libclc] [llvm] [openmp] [Clang] `__attribute__((assume))` refactor (PR #84934)

[Romaric Jodin via cfe-commits]

rjodinchr wrote:

It is only to tag functions. I guess the name would be `clspv_libclc_builtin` (https://github.com/llvm/llvm-project/blob/main/libclc/generic/include/clc/clcfunc.h#L11).

I've started to test with such a solution to make sure everything works on clspv side, but I need more time.

https://github.com/llvm/llvm-project/pull/84934