How to add a build phase in a project template?

After quite a lot of trial-and-error I've worked it out. This is the extra key needed in the TemplateInfo.plist. This adds a script that will run after the other default build phases.

<key>Targets</key>
<array>
    <dict>
        <key>BuildPhases</key>
        <array>
            <dict>
                <key>Class</key>
                <string>ShellScript</string>
                <key>ShellPath</key>
                <string>/bin/sh</string>
                <key>ShellScript</key>
                <string># Just a comment</string>
            </dict>
        </array>
    </dict>
</array>