[llvm] [JumpThreading] Thread over BB with only an unconditional branch (PR #86312)

[via llvm-commits]

dyung wrote:

@XChy your change seems to be causing a test failure of `llvm/test/CodeGen/Generic/live-debug-label.ll` on several buildbots:
- https://lab.llvm.org/buildbot/#/builders/183/builds/20800
- https://lab.llvm.org/buildbot/#/builders/188/builds/44495
- https://lab.llvm.org/buildbot/#/builders/245/builds/23249
- https://lab.llvm.org/buildbot/#/builders/280/builds/1949
- https://lab.llvm.org/buildbot/#/builders/119/builds/17315

Can you take a look and revert if you need time to investigate?

https://github.com/llvm/llvm-project/pull/86312