[clang] [Clang] Overflow Idiom Exclusions (PR #100272)

[Justin Stitt via cfe-commits]

JustinStitt wrote:

> Actually stuff like unsigned overflows are not UB.
> 
> Maybe instead of `-fno-sanitize-overflow-idioms` we convert into `unsigned-integer-overflow` into ` check group` so user can -fno-sanitize=-unsigned-integer-overflow

Right, unsigned overflow is well-defined. This isn't about the semantics of "undefined-ness". We want the unsigned sanitizer ON but some of the things it reports are noisy -- that's what this PR is about


https://github.com/llvm/llvm-project/pull/100272