<export> [optional, may be repeated] defines a build product of the project
that may be seen by other IDE projects or IDE features. Permits this project to
be used as a subproject of a plain Java project, for example.
<export>
<type>jar</type>
<location>${build.dir}/${build.jar}</location>
<!-- optional: <script>${home}/build.xml</script> -->
<build-target>jar</build-target>
<clean-target>clean</clean-target> <!-- optional -->
</export>
Declares that the file ${build.dir}/${build.jar} is to be exported as a JAR
build product of this project. (<type> should always be folder or jar for
use from plain Java projects, but other project types may define other kinds of
exports.) If used as a subproject of a plain Java project,
${build.dir}/${build.jar} will be added to the parent project’s classpath;
build-impl.xml in the parent project will call this project’s build.xml#jar when
"building dependencies", and build.xml#clean when "cleaning dependencies".