[llvm] [IR] Add TargetExtType::CanBeAlloca property (PR #99016)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

The use case here is specifically a type that *is* sized but cannot be used in alloca?

What about use in byval?

https://github.com/llvm/llvm-project/pull/99016