[clang] [clang] Catch missing format attributes (PR #70024)

[Aaron Ballman via cfe-commits]

================
@@ -936,6 +936,9 @@ def err_opencl_invalid_param : Error<
 def err_opencl_invalid_return : Error<
   "declaring function return value of type %0 is not allowed %select{; did you forget * ?|}1">;
 def warn_enum_value_overflow : Warning<"overflow in enumeration value">;
+def warn_missing_format_attribute : Warning<
+  "diagnostic behavior may be improved by adding the %0 format attribute to the declaration of %1">,
+  InGroup<MissingFormatAttribute>, DefaultIgnore;
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AaronBallman wrote:

```suggestion
  InGroup<DiagGroup<"missing-format-attribute">>, DefaultIgnore;
```

https://github.com/llvm/llvm-project/pull/70024