kotlin-fork/compiler/frontend/buildLexer.xml

<project name="JetLexer" default="lexer">
    <property name="home" value="${basedir}"/>
<!--
    This script relies on a custom JFlex that is available in the sources of IntelliJ IDEA Community Edition
    put the idea.properties file to the root directory of the frontend module, and put the following property there:

       idea.home=../../../idea/src

    where "../../../idea/src" is the relative location of the sources of IntelliJ IDEA Community
-->
    <property file="${home}/idea.properties"/>

    <property name="flex.base" value="${idea.home}/tools/lexer/jflex-1.4"/>
    <property name="out.dir" value="${basedir}/tmpout"/>

    <macrodef name="flex">
      <attribute name="flexfile"/>
      <attribute name="destdir"/>
      <attribute name="skeleton" default="${idea.home}/tools/lexer/idea-flex.skeleton"/>
      <sequential>
        <delete dir="${out.dir}"/>
        <mkdir dir="${out.dir}"/>
        <java classname="JFlex.Main"
              jvmargs="-Xmx512M"
              fork="true"
              failonerror="true">
          <arg value="-sliceandcharat"/>
          <arg value="-skel"/>
          <arg value="@{skeleton}"/>
          <arg value="-d"/>
          <arg value="${out.dir}"/>
          <arg value="@{flexfile}"/>
          <classpath>
            <pathelement location="${flex.base}/lib/JFlex.jar"/>
          </classpath>
        </java>
        <move todir="@{destdir}">
          <fileset dir="${out.dir}">
            <include name="*.java"/>
          </fileset>
        </move>
        <delete dir="${out.dir}"/>
      </sequential>
    </macrodef>

    <target name="lexer">
        <echo message="${flex.base}"/>
        <flex flexfile="${home}/src/org/jetbrains/jet/lexer/Jet.flex"
              destdir="${home}//src/org/jetbrains/jet/lexer/"/>
    </target>
</project>