[clang] [clang] Add clang::debug_info_type attribute for bitfields (PR #69104)

[David Blaikie via cfe-commits]

dwblaikie wrote:

> This is useful when user is forced to use the same type for all bitfields in a class to get better [layout](https://godbolt.org/z/ovWqzqv9x) and [codegen](https://godbolt.org/z/bdoqvz9e6) from MSVC

Does this issue not apply to other platforms? (I didn't think you could bitfield enums)

I'd think maybe rather than adding an attribute to workaround MSVC's missing support - code could #ifdef in a way that's ABI compatible, maybe? (though I admit that's a subtle thing to get right & the cost for getting it wrong is significant) 

https://github.com/llvm/llvm-project/pull/69104