[clang] [clang][sema] Add nonnull attribute to builtin format functions (PR #158626)

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@@ -67,6 +67,7 @@
 // The third value provided to the macro specifies information about attributes
 // of the function.  These must be kept in sync with the predicates in the
 // Builtin::Context class.  Currently we have:
+//  N -> nonnull
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Sirraide wrote:

This should document that this option takes arguments, similarly to `C` below.

https://github.com/llvm/llvm-project/pull/158626