解决ant编译中出现“includeantruntime was not set”警告的问题

ant编译报错如下：

compile:

    [javac] D:\workspace\bits_core\build.xml:70: warning: 'includeantruntime' was not set, defaulting to build.sysclasspath=last; set to false for repeatable builds

解决方法：只需要根据提示在javac任务中添加includeAntRuntime="false"属性即可。例如：
修改前：
    <javac srcdir="${srcDir}" destdir="${binDir}" />
修改后：
    <javac srcdir="${srcDir}" destdir="${binDir}" includeAntRuntime="false" />
注：
1.对于includeAntRuntime属性，官方的解释如下：
    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.此警告在较早的ant版本中可能不会出现，当前用的版本是：Apache Ant(TM) version 1.8.2 compiled on December 20 2010。所以此问题跟ant版本有关。