[llvm] add: hidden option to disable slow wasm pass (PR #67715)

[Alon Zakai via llvm-commits]

kripken wrote:

I haven't worked on this recently, so it might have changed, but back then it was not optional: later passes assumed control flow was reducible.

If that is still the case, another option here might be to see if the LLVM pass that removes irreducible control flow is faster than this (I expect it would be, since this pass works hard to find optimal shapes for wasm).

https://github.com/llvm/llvm-project/pull/67715