[clang] [clang][Modules] Keep existing global definition on type mismatch in GetOrCreateLLVMGlobal (PR #223877)

[Chuanqi Xu via cfe-commits]

ChuanqiXu9 wrote:

Oh, sorry. It seems that I am wrong. There shouldn't be duplicate decls so no merging is needed. 

For the patch itself, I still feel it is odd but if @efriedma-quic feel good, I won't object.

https://github.com/llvm/llvm-project/pull/223877