[clang] Thread safety analysis: Fix a bug in handling temporary constructors (PR #74020)

[Aaron Puchert via cfe-commits]

https://github.com/aaronpuchert commented:

I have some suggestions, but in principle this is absolutely right. Thanks for finding this and providing a fix!

>  The issue is that the map lives within a CFG block.

It didn't cross my mind to check how long `BuildLockset` lived, I always assumed it lived for the entire function. But you're right, it does not, and is therefore an unsuitable home for the map.

https://github.com/llvm/llvm-project/pull/74020