[clang] [C23] Accept an _Atomic underlying type (PR #147802)

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Halalaluyafail3 wrote:

> So we error by default, but still allow users to opt out of the error if they find they need to support an `_Atomic` underlying type.

Does clang normally reject some valid programs by default with a non-gnu standard selected, intentionally (i.e. not a bug)? If so, is there an option to turn all of these errors off? It seems like `-w` has no effect, it has to be specifically named `-Wno-underlying-atomic-qualifier-ignored`.

https://github.com/llvm/llvm-project/pull/147802