[llvm] [X86] Prevent NUW flag forwarding in ADD->SUB peephole (PR #201612)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

I'd say ditch this PR and start afresh if you believe you will be able to accomplish this in this release cycle (before mid Jan 2027)

https://github.com/llvm/llvm-project/pull/201612