[llvm] Add test for dwarf verification JSON output (PR #124936)

[Jacob Lalonde via llvm-commits]

Jlalond wrote:

> A follow up diff will modify the JSON and this ensures we can verify.

@youngdfb does this mean this test will fail on check-in? Or do you intend to extend this test after your future patch

https://github.com/llvm/llvm-project/pull/124936