[llvm] BPF: Ensure __sync_fetch_and_add() always generate atomic_fetch_add insn (PR #101428)

[Bryce Kahle via llvm-commits]

brycekahle wrote:

> x86_64 target may generate (e.g. jump table) which bpf back will not support

We avoid this by passing `-fno-jump-tables` (along with some other flags).

> when CORE is not available

This is the use case I'm talking about.

https://github.com/llvm/llvm-project/pull/101428