[llvm] Add unit test for CloneModule and #dbg_label (PR #91463)

[via llvm-commits]

PietroGhg wrote:

Hi @SLTozer, this test case is related to https://github.com/llvm/llvm-project/pull/91447 (and follow up PRs). For reference, the test case currently fails with `DICompileUnit not listed in llvm.dbg.cu`.

https://github.com/llvm/llvm-project/pull/91463