[clang] [Serialization] Stop demote var definition as declaration (#172430) (#177117) (PR #184287)

[Chuanqi Xu via cfe-commits]

ChuanqiXu9 wrote:

@boomanaiden154 I believe this won't affect you since I workaround cases for header modules.... not ideal but innocent after all. 

https://github.com/llvm/llvm-project/pull/184287