[libclc] [libclc] Add contract flag to native_recip (PR #179406)

[Wenju He via cfe-commits]

wenju-he wrote:

> I thought you switched the build to enable fast contract globally, and locally disabled it?

thanks, will continue to work on that in https://github.com/llvm/llvm-project/pull/153137. 
I see this particular case today and somehow forgot that pr.

Close this PR.

https://github.com/llvm/llvm-project/pull/179406