Update dita command example

[stefan-jung]

This snippet from /docsrc/samples/ant_sample/dita-cmd.xml should use the new propertyfile notation as explained on Building output using the dita command.

<macrodef name="dita-cmd">
  <attribute name="input"/>
  <attribute name="format"/>
  <attribute name="propertyfile"/>
  <sequential>
    <exec executable="${dita.dir}/bin/dita">
      <arg line="-i @{input} -f @{format} -propertyfile @{propertyfile}"/>
    </exec>
  </sequential>
</macrodef>

should be changed to

<macrodef name="dita-cmd">
  <attribute name="input"/>
  <attribute name="format"/>
  <attribute name="propertyfile"/>
  <sequential>
    <exec executable="${dita.dir}/bin/dita">
      <arg line="-i @{input} -f @{format} --propertyfile=@{propertyfile}"/>
    </exec>
  </sequential>
</macrodef>

[infotexture]

@xephon2 Thanks, good catch. 👍

We try to use the GNU double-hyphen syntax for CLI options throughout the docs, so I'll also switch to --input and --format here.