[llvm] [llvm-dwarfdump] Make --verify for .debug_names multithreaded. (PR #127281)

[Alexander Yermolovich via llvm-commits]

ayermolo wrote:

> Might be good to have to specify using multiple threads when verifying. So maybe opt into multi-threaded output to maintain deterministic output by default and allowing users to opt into non-deterministic output for speed? Something like
> 
> ```
> --verify-multithreaded
> ```
> 
> If this is specified, then we can take full advantage of the speed at the cost of non-deterministic output.

I added a flag:
--verify-num-threads.
It defaults to system number of threads.
Instead set it to 1?

https://github.com/llvm/llvm-project/pull/127281