[clang] [CIR] Disable CIR pipeline for LLVM IR inputs (PR #187729)

[Fangrui Song via cfe-commits]

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@@ -0,0 +1,16 @@
+// Verify that -fclangir is always forwarded to -cc1 by the driver, and
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MaskRay wrote:

We should have regular -fclangir  clang/test/Driver tests. Then we can add the test to that file, instead of creating this new file `clangir-no-llvmir.c`

https://github.com/llvm/llvm-project/pull/187729