[llvm] [PGO] Preserve analysis results when nothing was instrumented (PR #93421)

[Pavel Samolysov via llvm-commits]

samolisov wrote:

@teresajohnson This is my bad, I should have used the re-request review button.

Anyway, thank you very much for review. I'm going to merge this after CI finishing.

https://github.com/llvm/llvm-project/pull/93421