[llvm] [X86] Don't rely on global contraction flag (PR #167252)

[Mikołaj Piróg via llvm-commits]

mikolaj-pirog wrote:

> Should we warn `fp-contract` is not used on X86?

It's not used by the X86 backend, but target independent code still uses it, so IR without `contract` on IR but with `--fp-contract=fast` on CLI may still emit FMA in the end

https://github.com/llvm/llvm-project/pull/167252