[llvm] [clang] [Clang] Correct __builtin_dynamic_object_size for subobject types (PR #78526)

[Nikita Popov via cfe-commits]

https://github.com/nikic requested changes to this pull request.

Using anything but the size and alignment of the alloca type in a way that affects program semantics is illegal.

https://github.com/llvm/llvm-project/pull/78526