[llvm] [DebugInfo] Fix line 0 records incorrectly having is_stmt set (PR #166627)

[Orlando Cazalet-Hyams via llvm-commits]

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OCHyams wrote:

As mentioned in a comment earlier, I feel like it's probably a bug if scope line is zero. But if we keep the other check for scope line in this patch, for completeness sake it should probably be replicated here.

https://github.com/llvm/llvm-project/pull/166627