[llvm] Allow 128-bit discriminants in DWARF variants (PR #125578)

[via llvm-commits]

beetrees wrote:

I don't think there's anything you need to do here: according the the guide all that needs to happen to request a backport is for someone who can edit PR milestones to add this PR (or the issue) to the [LLVM 20.X Release milestone](https://github.com/llvm/llvm-project/milestone/26) (maybe @dwblaikie is able to do that? I don't know which permissions are required) and then I can comment "/cherry-pick 3c2807624d2006fa8aacf9c6441c9a3034a52b44 34929853bc39d28943373b8a96371a7e81e98917" which will make @llvmbot automatically create a backport pull request.

https://github.com/llvm/llvm-project/pull/125578