[clang] [Serialization] Fix lazy template loading (PR #133057)

[Jonas Hahnfeld via cfe-commits]

hahnjo wrote:

Invested some time today and I think the fix is https://github.com/llvm/llvm-project/pull/154158. It works for the reproducer posted in https://github.com/llvm/llvm-project/pull/133057#issuecomment-2886816972, @ilya-biryukov or @emaxx-google if you have some time, would it be possible to test the two PRs together in your infrastructure?

https://github.com/llvm/llvm-project/pull/133057