[llvm] [SimplifyCFG] Skip threading if the target may have divergent branches (PR #100185)

[via llvm-commits]

hiraditya wrote:

Maybe jump threading can have flags to do 'lightweight' threading (that subsumes what SimplifyCFG does with a simple cost model)? This way we have the code in one place.

https://github.com/llvm/llvm-project/pull/100185