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

[Greg Clayton via llvm-commits]

https://github.com/clayborg approved this pull request.

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.

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