should we delete lib folder when we clean project in java and how to build it again after delete lib folder using apache ant and ivy

I have some problem, in my friend's code there is a clean code using apache ant seems to delete lib folder as well. but when I try to create project, it fails because the lib folder is missing. then how to build the correctly using ant apache ?

this is clean code

<target name="clean" description="--> clean the project">
            <delete includeemptydirs="true">
                <fileset dir="${basedir}">
                    <exclude name="src/**" />
                    <exclude name="build.xml" />
                  <exclude name="ivy.xml" />
                </fileset>
            </delete>
        </target>

and this build code

<target name="build" description="Compile main source tree java files">
        <mkdir dir="${build.dir}" />

        <javac srcdir="${java.dir}" destdir="${build.dir}" classpathref="lib.path.id" debug="true" deprecation="true" optimize="true" failonerror="true" />
        <!-- class path properties files -->
        <copy file="${resource.dir}/log4j.properties" todir="${build.dir}" />
        <copy file="${resource.dir}/mncplaymedia.properties" todir="${build.dir}" />
        <copy todir="${build.dir}">
            <fileset dir="${resource.dir}" />
        </copy>
        
    </target>

thank you

I think you have to build this project, then put the war or jar file in webapps on your web server (like jetty, tomcat and etc.)