[llvm] Modify llvm-gsymutil to ignore invalid file indexes. (PR #70876)

[Greg Clayton via llvm-commits]

clayborg wrote:

> Given this is about LLVM project's compatibility with other LLVM projects, it does feel like fixing the root cause would be good - though I don't fundamentally object to making tools more robust to unexpected inputs.

Agreed!

> It'd be good to at least get test cases and bugs filed for the cases where this is a problem, perhaps?

I am also on board with this. Often times the LTO bugs and or BOLT issues are hard to reduce to a small enough test case to make them happen. But I am all for filing bugs using a reduced test case for any cases where DWARF is compromised.

https://github.com/llvm/llvm-project/pull/70876