ant调用外部ant，并变编译项目,无法找到rt.jar的处理方法

xml version="1.0" encoding="UTF-8"?>
<project name="catwalk" default="build" basedir=".">
    <description>
        catwalk build file
    description>
    <property name="base.src" value="src/java"/>
    <property name="build.pro" value="build/catwalk_exploded"/>
    <property name="build.classes" value="${build.pro}/WEB-INF/classes"/>
    <property name="build.resource" value="${build.pro}/WEB-INF/classes/resource"/>
    <property name="build.lib" value="${build.pro}/WEB-INF/lib"/>
    <property name="lib" value="../lib"/>
    <property name="fw" value="../fw"/>
    
    <target name="clean" description="clean up">
        <delete dir="${build.pro}/classes"/>
    target>
    
    <target name="init">
        <mkdir dir="build"/>
        <mkdir dir="${base.src}"/>
        <mkdir dir="${build.resource}"/>
        <mkdir dir="${build.lib}"/>
    target>

    
    <target name="compile" depends="copy-jar"  description="compile the source">
        <javac srcdir="${base.src}" destdir="${build.classes}" includejavaruntime="false" encoding="utf-8" debug="true">
            <classpath>
                <fileset dir="${build.lib}">
                    <include name="**/*.jar"/>
                fileset>
            classpath>
            <compilerarg value="-XDignore.symbol.file"/>
            
        javac>
    target>
    <target name="build" depends="compile" description="build catwalk">

    target>
    <target name="fw-compile" depends="init" description="compile and copy fw jar to lib">
        <ant antfile="build.xml" dir="${fw}"/>
    target>
    <target name="copy-jar" depends="fw-compile" description="copy dependent jar to lib">
        <copy file="${fw}/dist/fw.jar" todir="${build.lib}"/>
        <copydir src="${lib}" dest="${build.lib}"/>
        <copydir src="src/resource/" dest="${build.classes}"/>
        <copy todir="${build.pro}">
            <fileset dir="WebContent">
                <exclude name="WEB-INF/classes/resource/**"/>
                <exclude name="reportTemplate/**"/>
                <exclude name="bank/**"/>
                <exclude name="WEB-INF/upload/**"/>
                <exclude name="WEB-INF/bank/**"/>
            fileset>
        copy>
    target>
project>