[llvm] Mark test as XFAIL that started failing after 418f0066eb. (PR #85027)

[Orlando Cazalet-Hyams via llvm-commits]

OCHyams wrote:

I'm not entirely sure why the issue is popping up now after 418f0066eb (I guess the change to the `test_debuginfo.pl` script dislodged a silent failure, now that the debugger return value is examined?). Either way, given the failure message and how we've dealt with it in the past, this LGTM.

https://github.com/llvm/llvm-project/pull/85027