[llvm] [offload] add nodiscard support to offload-tblgen and mark olInit (PR #209727)

[Joseph Huber via llvm-commits]

jhuber6 wrote:

To be fair, I think the HIP headers do this, but I'm unsure if it's worthwhile because these are supposed to be C headers and C23 is fairly new.

https://github.com/llvm/llvm-project/pull/209727