[llvm] [NFC][Coverage] Do not use recursion for GCOV propagateCounts. (PR #68455)

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shen3qing1 wrote:

Hey @jroelofs thanks for LGTM! But I don't have permission to merge this change :< 
![image](https://github.com/llvm/llvm-project/assets/145069838/8826c676-5c19-4469-9279-32041614af1a)

https://github.com/llvm/llvm-project/pull/68455