[clang] [Serialization] Load Specializations Lazily (PR #76774)

[Jonas Hahnfeld via cfe-commits]

hahnjo wrote:

As far as I can tell from https://github.com/llvm/llvm-project/pull/76774#issuecomment-1914177330 above, the last push only changed the default value of `LoadExternalSpecializationsLazily`. In that case, my test results from https://github.com/llvm/llvm-project/pull/76774#issuecomment-1912182171 remain fully valid, especially

> Switching the new `LoadExternalSpecializationsLazily` to disabled by default (somehow the argument didn't work on its own) instead crashes, most of the cases involving `MultiOnDiskHashTable`. I suspect some kind of memory error maybe?

https://github.com/llvm/llvm-project/pull/76774