[llvm] [llvm-profgen][SPGO] Support profiles with multiple concurrent processes (PR #169353)

[via llvm-commits]

https://github.com/HighW4y2H3ll requested changes to this pull request.

The intention of multiple pid feels abit unsound to me. There’s only one binary but multiple samples that maybe coming from binaries that have different base addresses or slight variations? If the binary forks directly, the address space shall be exactly the same? But then the question is why do we even need pid at all? Maybe we should just get rid of pid instead?

https://github.com/llvm/llvm-project/pull/169353