[llvm] [DiagnosticInfo] Output full file path instead of relative path (PR #68027)

[Florian Hahn via llvm-commits]

fhahn wrote:

> LTO remark dumps always output the relative path, which causes inconsistent behavior if the input path is absolute path (since preLTO stage would output absolute path).

Is it possible this difference is due to how the options are passed through to LTO/how things are configured at the LTO plugin level?

https://github.com/llvm/llvm-project/pull/68027