[llvm] [VPlan] Update final exit value via VPlan. (PR #112147)

[Florian Hahn via llvm-commits]

fhahn wrote:

Updated based on latest version of https://github.com/llvm/llvm-project/pull/112145, should be good for a first look, but probably best to wrap up https://github.com/llvm/llvm-project/pull/112145 first

https://github.com/llvm/llvm-project/pull/112147