[llvm] [BranchFolding] Fold away subsequent identical branches (PR #203110)

[Aiden Grossman via llvm-commits]

boomanaiden154 wrote:

We should be able to get around problems with multiple predecessors of the current BB by just deleting the terminator branch from the previous block.

Subsequent identical unconditional branches look like they might get produced afterwards and either way are probably better to handle in a separate patch.

https://github.com/llvm/llvm-project/pull/203110