In order to make tooling around dwarf health easier, I've added an
`--json-summary-file` option to `llvm-gsymutil` that will spit out error
summary data with counts to a JSON file.
I've added the same capability to `llvm-dwarfdump` in a [different
PR.](https://github.com/llvm/llvm-project/pull/81762)
The format of the json is:
```JSON
{
"error-categories": {
"<first category description>": {"count": 1234},
"<next category description>": {"count":4321}
},
"error-count": 5555
}
```
for a clean run:
```JSON
{
"error-categories": {},
"error-count": 0
}
```
---------
Co-authored-by: Kevin Frei <freik@meta.com>
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