[clang] [Clang] Add -fwrapv-pointer flag (PR #122486)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

I am a bit concerned about the behavioral change, but given the more aggressive optimizations in LLVM 20, I think it makes sense to get this into Clang 20 to see what the fallout is during early RCs. If there's negative impact, we can consider cherry-picking a revert from the branch. Matching GCC's behavior for the options seems like a defensible approach.

https://github.com/llvm/llvm-project/pull/122486