[llvm] [IR] Fix User use-after-destroy by zapping in ~User (PR #170575)

[Nikita Popov via llvm-commits]

nikic wrote:

@boomanaiden154 I believe MDNode has been fixed by https://github.com/llvm/llvm-project/commit/2740c1875d1c6d6b78baf4f8215e36362ca0e98c already.

https://github.com/llvm/llvm-project/pull/170575