[clang] [clang][CodeGen] Zero init unspecified fields in initializers in C (#97459) (PR #97121)

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yabinc wrote:

@efriedma-quic, Thanks for the suggestion!
I have created a new bug in https://github.com/llvm/llvm-project/issues/97459, and also updated commit message to clarify that this is needed by the linux kernel instead of c23 standard.

https://github.com/llvm/llvm-project/pull/97121