[clang] [CodeGen][CIR] Split out Backend Diags to utils, impl CIR error-attr (PR #225966)

[Andy Kaylor via cfe-commits]

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@@ -12,6 +12,7 @@
 #include "clang/CodeGen/BackendUtil.h"
 #include "clang/CodeGen/CodeGenAction.h"
 #include "clang/CodeGen/ModuleLinker.h"
+#include "clang/CodeGenUtils/BackendDiagnosticHandler.h"
 
 #include "llvm/IR/DiagnosticInfo.h"
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andykaylor wrote:

This is now unused.

https://github.com/llvm/llvm-project/pull/225966