[llvm] [StructurizeCFG] nested-if zerocost hoist bugfix (PR #155408)

[Shilei Tian via llvm-commits]

shiltian wrote:

Can you run a full CQE cycle before landing this PR? StructurizeCFG is very sensitive to changes and can easily cause regressions in downstream testing. I suggest being proactive when touching it.

https://github.com/llvm/llvm-project/pull/155408