[llvm] [IR] Add nowrap flags for trunc instruction (PR #85592)

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

> > * [ ]   Add the support for dropping nsw/nuw flags to `llvm-reduce`
> 
> I've already implemented this but haven't had working internet to push it

Ping?

https://github.com/llvm/llvm-project/pull/85592