I ended up solving this problem recently. The first step is to ensure that the builder is set to use a "Separate JRE" (Zend Studio's). The second step was to update my buildfile to the following:
<?xml version="1.0" encoding="UTF-8"?>
<project basedir="." default="sass">
<target name="sass">
<exec osfamily="windows" vmlauncher="false" executable="sass">
<arg value="--update" />
<arg value="scss/:css/" />
<arg value="--style=compressed" />
</exec>
</target>
</project>
The key was to set the vmlauncher
attribute to false
on Windows.