How to include additional compiler arguments when using mxmlc ant task

I'm not sure if this will help you out but when you check that option using flex builder it updates the .actionScriptProperties file:

<compiler additionalCompilerArguments="-locale en_US" copyDependentFiles="true">
<compilerSourcePath/>
</compiler>

setting the copyDependentFiles to true or false turns this on and off

You can all just copy the directory over but this doesn't remove the embedded files.

<copy todir="${SRC_DIR}/assets">
<fileset dir="${DEPLOY_DIR}">
</fileset>
</copy>

I believe it's

   <target...>
     <mxmlc...>
         <fonts>
            <manager class="flash.fonts.AFEFontManager"/>
         </fonts>

It's annoying that the documentation stops short of letting you actually figure out how to use the elements... an example or two would make a world of difference over at Adobe.