SDK: Add a Makefile to build the C++ stuff.

sdk_build/data/cpp/cpp.sdk

Index: sdk_build/data/cpp/cpp.sdk
diff --git a/sdk_build/data/cpp/cpp.sdk b/sdk_build/data/cpp/cpp.sdk
index 0a4b46bcbb2a706f7a70458af2e8480309822431..64a1e63bb234c27c3f29a06d0e75865cb7a560ff 100644
--- a/sdk_build/data/cpp/cpp.sdk
+++ b/sdk_build/data/cpp/cpp.sdk
@@ -4,7 +4,7 @@
 
 # This file contains steps for "building" a C/C++ SDK. It is processed by
 # //mojo/sdk_build/build_sdk.py.
-# TODO(vtl): This isn't done yet.
+# TODO(vtl): This isn't done yet. (Or is it?)
 
 import re
 
@@ -66,7 +66,8 @@ CopyDir("mojo/public/python/mojo_bindings",
 # Scripts to download binaries.
 CopyFiles(["sdk_build/data/common/download_file_from_google_storage.py",
            "sdk_build/data/common/download_mojom_tool.sh",
-           "sdk_build/data/cpp/download_clang.sh"],
+           "sdk_build/data/cpp/download_clang.sh",
+           "sdk_build/data/cpp/setup.sh"],
           "mojo_sdk_setup")
 
 # Figure out the version of clang, and include that. (This is a little janky,
@@ -86,3 +87,6 @@ CopyDir("examples/hello_mojo",
         "examples/hello_mojo",
         recursive=True,
         exclude_file_patterns=EXCLUDE_FILES)
+
+# Put in a simple example Makefile (in the root directory).
+CopyFiles("sdk_build/data/cpp/Makefile", "")