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

[Sven van Haastregt via llvm-commits]

svenvh wrote:

> It allows the source to be parsed, but then I don't see the attribute in the LLVM IR generated for libclc.

You will need to also convert the attribute into an LLVM IR construct (e.g. metadata) in Clang CodeGen.  See `CodeGenFunction::EmitKernelMetadata` for inspiration for example.

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