Codegen: Given a carbon file prints the assembly to the stdout (#2944)

Co-authored-by: Farzana Ahmed Siddique <fasiddique@google.com>

toolchain/codegen/codegen.h

@@ -0,0 +1,22 @@
+// 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
+
+#ifndef CARBON_TOOLCHAIN_CODEGEN_CODEGEN_H_
+#define CARBON_TOOLCHAIN_CODEGEN_CODEGEN_H_
+
+#include <cstdint>
+
+#include "llvm/IR/Module.h"
+
+namespace Carbon {
+// Prints the assembly to stdout for the given llvm module.
+// If print fails, this returns false and any information about the failure is
+// printed to the error stream.
+auto PrintAssemblyFromModule(llvm::Module& module,
+                             llvm::StringRef target_triple,
+                             llvm::raw_pwrite_stream& error_stream,
+                             llvm::raw_pwrite_stream& output_stream) -> bool;
+}  // namespace Carbon
+
+#endif  // CARBON_TOOLCHAIN_CODEGEN_CODEGEN_H_