如何使用Vaadin 7和maven编译其他非主题SCSS文件

<build>
    <plugins>
        <plugin>
            <groupId>com.vaadin</groupId>
            <artifactId>vaadin-maven-plugin</artifactId>
            <version>7.7.13</version>
            <executions>
                <execution>
                    <goals>
                        <goal>update-theme</goal>
                        <goal>compile-theme</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

<plugin>
    <groupId>com.vaadin</groupId>
    <artifactId>vaadin-maven-plugin</artifactId>
    <version>7.7.13</version>
    <configuration>
        <extraJvmArgs>-Xmx512M -Xss1024k</extraJvmArgs>
        <webappDirectory>${basedir}/src/main/webapp/VAADIN/widgetsets</webappDirectory>
        <draftCompile>false</draftCompile>
        <compileReport>true</compileReport>
        <style>${basedir}/src/main/webapp/VAADIN/themes/mytheme/custom.scss</style>
    </configuration>
</plugin>

mvn vaadin:update-theme vaadin:compile-theme