[clang] Reland "[clang] Add nuw attribute to GEPs (#105496)" (PR #107257)

[Nikita Popov via cfe-commits]

nikic wrote:

@sbc100 That wasm is not necessarily a miscompile, it may be UB in the source program, if it uses a negative number in an *unsigned* variable to index an array. Is the affected code clean under ubsan? (See https://github.com/llvm/llvm-project/issues/108770 for a similar report that was due to UB.)

https://github.com/llvm/llvm-project/pull/107257