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

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Sirraide wrote:

> I'm not sure if this diagnostic information makes sense, do you have any suggestions?

If passing a specific command-line to Clang causes it to assert, then I’d say issuing a diagnostic instead is better, yeah (if this assert was only reachable by using Clang as a library then it’d be a different matter imo), so I think it does make sense, yeah.

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