[llvm] [DWARFVerifier] Fix debug_str_offsets DWARF version detection (PR #81303)

[Felipe de Azevedo Piovezan via llvm-commits]

felipepiovezan wrote:

>  Does the yaml encoding not support dwo sections?

Sadly, this is the reason! The encodings are tiny enough that I think they are still legible though (`debug_str_dwo` and `dwo_str_offsets` are just a sequence of 4-byte offsets, `debug_

> - the test looks like it did work to test the functionality as it was before this patch (where str_offsets and str_offsets.dwo were treated the same

Sorry, I think I used too strong of a wording there, I will rephrase it in the commit message. This comment on the other review made me be a bit too literal on "dwo is not tested":

> The legacy DWARFv4 Split DWARF mode str offsets format can only appear in .dwo files 

In this sense, the test was finding an error through an unintended path, and the `dwo` path of the code was never exercised.

https://github.com/llvm/llvm-project/pull/81303