[llvm] Implement missing clone in EVL recipe (PR #206964)

[Luke Lau via llvm-commits]

lukel97 wrote:

> > Is this needed for some sort of VPlan cloning downstream? I don't think this gets exercised upstream since we don't unroll EVL tail folded loops
> 
> Yes, It is blocking VPlan cloning.

Can you elaborate on what exactly you need this for downstream, and if you plan on eventually upstreaming it? Otherwise I'm not sure its worthwhile having dead code in tree

https://github.com/llvm/llvm-project/pull/206964