[llvm] Gsymutil aggregation similar to DwarfDump --verify (PR #81154)

[Kevin Frei via llvm-commits]

kevinfrei wrote:

> As long as the test suite runs fine:
> 
> ```
> ./bin/llvm-lit -sv llvm/test/tools/llvm-gsymutil
> ```
> 
> And the `DebugInfoGSYMTests` unit test binary runs fine, this all LGTM now.

Yup. Everything is clean (I had to make a few changes to the unit test binary that you'll see in the diff). I've been running full `check-llvm` because I'm lazy and didn't want to accidentally miss a test.

https://github.com/llvm/llvm-project/pull/81154