[clang] [Clang] raise extension warning for unknown namespaced attributes (PR #120925)

[Erich Keane via cfe-commits]

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@@ -179,6 +179,8 @@ def err_opencl_unknown_type_specifier : Error<
 
 def warn_unknown_attribute_ignored : Warning<
   "unknown attribute %0 ignored">, InGroup<UnknownAttributes>;
+def ext_unknown_attribute_ignored : Extension<
+  "unknown attribute %0 ignored">, InGroup<UnknownAttributes>;
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erichkeane wrote:

the text here should be different, we need to say something about how we don't know it because we don't support the whole namespace.

Also, I don't think this makes sense as an extension warning, we should diagnose unknown namespace, but it isn't any different than unknown attribute in severity.

https://github.com/llvm/llvm-project/pull/120925