[llvm] [PGO][profcheck] ignore explicitly cold functions (PR #151778)

[Mircea Trofin via llvm-commits]

mtrofin wrote:

### Merge activity

* **Aug 4, 1:52 AM UTC**: A user started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/151778).


https://github.com/llvm/llvm-project/pull/151778