[clang] [clang] Accept empty enum in MSVC compatible C (PR #159981)

[via cfe-commits]

yicuixi wrote:

> I think emitting two diagnostics is fine (one for the underlying type and one for the empty enum) because they are separate extensions. But I think it's a bit odd that we claim the underlying type is a Microsoft extension rather than a C23 extension -- that seems to be a preexisting issue which could be handled in a separate PR: https://godbolt.org/z/sMhGoE3qq

SGTM, I'd prefer to fix that in a separate patch.

https://github.com/llvm/llvm-project/pull/159981