Use AST to start inserting fn (#530)

migrate_cpp/cpp_refactoring/BUILD

@@ -0,0 +1,16 @@
+# Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+# Exceptions. See /LICENSE for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+load("@rules_cc//cc:defs.bzl", "cc_binary")
+
+package(default_visibility = ["//visibility:public"])
+
+cc_binary(
+    name = "cpp_refactoring",
+    srcs = ["main.cpp"],
+    deps = [
+        "@llvm-project//clang:ast_matchers",
+        "@llvm-project//clang:tooling",
+    ],
+)