Using a python script to build sepolicy

Current sepolicy CIL files are built by several command-line tools
in Android.mk. This change extracts some of the build logic into a
python script to relief the effort in Android.mk.

The first command is `build_sepolicy build_cil`. It's possible to add
more sub-commands under the build_sepolicy script in the future.

Bug: 64240127
Test: build bullhead/taimen
Change-Id: Ie0ae4fc5256a550c72954cde5d5dd213a22d159a
diff --git a/build/Android.bp b/build/Android.bp
new file mode 100644
index 0000000..d3f1fc3
--- /dev/null
+++ b/build/Android.bp
@@ -0,0 +1,34 @@
+// Copyright (C) 2018 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+python_binary_host {
+  name: "build_sepolicy",
+  srcs: [
+    "build_sepolicy.py",
+    "file_utils.py",
+  ],
+  required: [
+    "checkpolicy",
+    "secilc",
+    "version_policy",
+  ],
+  version: {
+    py2: {
+      enabled: true,
+    },
+    py3: {
+      enabled: false,
+    },
+  },
+}