[clang] [Clang] disallow # operators in attribute argument lists (PR #147308)

[Aaron Ballman via cfe-commits]

================
@@ -830,6 +830,8 @@ def err_ms_property_expected_comma_or_rparen : Error<
   "expected ',' or ')' at end of property accessor list">;
 def err_ms_property_initializer : Error<
   "property declaration cannot have a default member initializer">;
+def err_invalid_attribute_argument
+    : Error<"'%0' is not allowed in attribute argument lists">;
----------------
AaronBallman wrote:

```suggestion
    : Error<"'%0' is not allowed in an attribute argument list">;
```

https://github.com/llvm/llvm-project/pull/147308