[llvm] [llvm-objcopy][COFF] Update .symidx values after stripping (PR #153322)

[James Henderson via llvm-commits]

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@@ -0,0 +1,225 @@
+## Bail out if a section consisting of symidx is invalid.
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jh7370 wrote:

```suggestion
## Test that we bail out if a section consisting of symidx is invalid.
```
Is "symidx" a spec-defined name? If not, I'd just write it as "symbol indices".

https://github.com/llvm/llvm-project/pull/153322