[llvm] [RFC][utils] Add script to update failed tests (PR #131637)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

There was https://github.com/llvm/llvm-project/pull/108425, which added an `--update-tests` option to lit. Lit knows the correct build directory to use.

It was reverted, but I don't know why. @hnrklssn?

https://github.com/llvm/llvm-project/pull/131637