[clang] [clang]Implement the c23 stdc bit builtins (PR #185978)

[Aaron Ballman via cfe-commits]

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@@ -0,0 +1 @@
+#include "../../CodeGen/Inputs/stdbit.h"
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AaronBallman wrote:

Erm, I think Sema tests should be independent of codegen tests, so I'm not certain this is a good idea (though I understand the desire to not duplicate the test file, too).

https://github.com/llvm/llvm-project/pull/185978