[clang] [llvm] [clang][Modules][Serialization] Avoid serializing duplicate source location entries for shared input files (PR #209795)

[Corentin Jabot via cfe-commits]

https://github.com/cor3ntin commented:

Did look up in the bug tracker which issues would be addressed by this change?

https://github.com/llvm/llvm-project/pull/209795