[clang] [CIR] Build out AST consumer patterns to reach the entry point into CIRGen (PR #91007)

[Bruno Cardoso Lopes via cfe-commits]

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@@ -0,0 +1,88 @@
+//===--- CIRGenAction.cpp - LLVM Code generation Frontend Action ---------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/CIRFrontendAction/CIRGenAction.h"
+#include "clang/CIR/CIRGenerator.h"
+#include "clang/Frontend/CompilerInstance.h"
+
+#include "mlir/IR/MLIRContext.h"
+#include "mlir/IR/OwningOpRef.h"
+
+using namespace cir;
+using namespace clang;
+
+namespace cir {
+
+class CIRGenConsumer : public clang::ASTConsumer {
+
+  virtual void anchor();
+
+  [[maybe_unused]] CIRGenAction::OutputType action;
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bcardosolopes wrote:

To silence warnings for things we are about to introduce in follow up commits. Sometimes we prefetch the skeleton in NFC fashion, in order to make functionality changes have a smaller / more relevant diff. But we could surely remove them too. 

https://github.com/llvm/llvm-project/pull/91007