build.xml

<?xml version="1.0" encoding="UTF-8"?>
<project name="VpnReverseTether" default="help">
  <property file="local.properties" />
  <property file="ant.properties" />
  <property environment="env" />

  <condition property="sdk.dir" value="${env.ANDROID_HOME}">
    <isset property="env.ANDROID_HOME" />
  </condition>

  <loadproperties srcFile="project.properties" />

  <!-- quick check on sdk.dir -->
  <fail
    message="sdk.dir is missing. Make sure to generate local.properties using 'android update project' or to inject it through the ANDROID_HOME environment variable."
    unless="sdk.dir"
  />

  <import file="${sdk.dir}/tools/ant/build.xml" />
</project>