Add support to extend commands bpfix and androidmk

Allows our partners to maintain partner-specific fixes in their repos. Converts most of androidmk into a library similar to bpfix. Makes some methods and types public for use by extended versions.

Bug:140727544
Test: Ran unit test cases &&
  ran test conversions with sample
Change-Id: I7e1fbf3a6a7a8bd47334f43fe3eb68cbbd3426c1
diff --git a/androidmk/cmd/androidmk.go b/androidmk/cmd/androidmk.go
new file mode 100644
index 0000000..00488eb
--- /dev/null
+++ b/androidmk/cmd/androidmk.go
@@ -0,0 +1,56 @@
+// Copyright 2017 Google Inc. All rights reserved.
+//
+// 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.
+
+package main
+
+import (
+	"bytes"
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"os"
+
+	"android/soong/androidmk/androidmk"
+)
+
+var usage = func() {
+	fmt.Fprintf(os.Stderr, "usage: androidmk [flags] <inputFile>\n"+
+		"\nandroidmk parses <inputFile> as an Android.mk file and attempts to output an analogous Android.bp file (to standard out)\n")
+	flag.PrintDefaults()
+	os.Exit(1)
+}
+
+func main() {
+	flag.Usage = usage
+	flag.Parse()
+	if len(flag.Args()) != 1 {
+		usage()
+	}
+	filePathToRead := flag.Arg(0)
+	b, err := ioutil.ReadFile(filePathToRead)
+	if err != nil {
+		fmt.Println(err.Error())
+		return
+	}
+
+	output, errs := androidmk.ConvertFile(os.Args[1], bytes.NewBuffer(b))
+	if len(errs) > 0 {
+		for _, err := range errs {
+			fmt.Fprintln(os.Stderr, "ERROR: ", err)
+		}
+		os.Exit(1)
+	}
+
+	fmt.Print(output)
+}