1.對于includeAntRuntime屬性，官方的解釋如下：
Whether to include the Ant run-time libraries in the classpath; defaults to yes, unless build.sysclasspath is set. It is usually best to set this to false so the script's behavior is not sensitive to the environment in which it is run.
2.此警告在較早的ant版本中可能不會出現。
<javac includeantruntime="false" srcdir="${src.dir}" destdir="${classes.dir}" />
