[llvm-branch-commits] [clang] [Serialization] Code cleanups and polish 83233 (PR #83237)

[Ilya Biryukov via llvm-branch-commits]

ilya-biryukov wrote:

I had to replicate what our build was doing very thoroughly, the exact PCMs each build action receives were important.
Here's the repro: [maps.tgz](https://github.com/user-attachments/files/16992332/maps.tgz). Just like last time, it works without the patch and starts failing with the patch.


https://github.com/llvm/llvm-project/pull/83237