[llvm] Give a warning when no dwo files are provided (PR #94336)

[Jinjie Huang via llvm-commits]

Labman-001 wrote:

Thank you for the suggestion. I have changed it to compile a non-split-dwarf binary from the source code only, so that it does not contain any skeleton information. Originally, I introduced the .s file to modify the skeleton in the split-dwarf binary to trigger an error when the corresponding .dwo file could not be found (but this does not seem to be my target scenario?), so I have removed it.
>  https://llvm.org/docs/TestingGuide.html#elaborated-tests 

btw,  it seems I couldn't  find `llvm/utils/update_test_body.py` in this guide, only `update_test_checks.py` and `update_test_prefix.py`were found.


https://github.com/llvm/llvm-project/pull/94336