[sledge] Protect against nonexistent paths in debug info
[sledge] Protect against nonexistent paths in debug info

Summary: Do not fail when resolving the realpath of a debug info path.

Reviewed By: jvillard

Differential Revision: D24746237

fbshipit-source-id: b9dc35176

jvillard/infer,facebook/infer,facebook/infer,facebook/infer,facebook/infer,jvillard/infer,jvillard/infer,facebook/infer,jvillard/infer,jvillard/infer,facebook/infer,jvillard/infer,facebook/infer,jvillard/infer