[clang] [Clang] Diagnose apply AST consume actions on LLVM IR (PR #88602)

[via cfe-commits]

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@@ -370,4 +370,7 @@ def warn_missing_symbol_graph_dir : Warning<
   "Missing symbol graph output directory, defaulting to working directory">,
   InGroup<ExtractAPIMisuse>;
 
+def err_ast_action_on_unparsable_source : Error<
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Sirraide wrote:

nit: Maybe a different name for this would be better? It’s not really ‘unparseable’, seeing as we can parse LLVM IR just fine; it’s just not C++. 

https://github.com/llvm/llvm-project/pull/88602