[llvm] [BOLT] Preserve interprocedural fall-throughs (PR #219430)

[via llvm-commits]

Thrrreeee wrote:

Great fix! I encountered a similar issue while optimizing libc.so with BOLT, such as: 
<img width="1280" height="779" alt="image" src="https://github.com/user-attachments/assets/5c0ab95f-8b6b-4d20-9a78-e57e61003067" />

In this case, BOLT may incorrectly optimize the code when` --split-functions`.


https://github.com/llvm/llvm-project/pull/219430