[clang] [OpenACC][Sema] Implement warning for non-effective 'private' (PR #149004)

[Erich Keane via cfe-commits]

================
@@ -13478,6 +13478,12 @@ def err_acc_invalid_default_type
 def err_acc_device_type_multiple_archs
     : Error<"OpenACC 'device_type' clause on a 'set' construct only permits "
             "one architecture">;
+def warn_acc_var_referenced_lacks_op
+    : Warning<"variable of type %0 referenced in OpenACC '%1' clause does not "
----------------
erichkeane wrote:

Yes, it is not 'ill-formed' by the standard, there is no requirement in the standard to have constructors/destructors/etc, as far as I can tell, so I left it as 'warning-as-default-error'.

https://github.com/llvm/llvm-project/pull/149004