You should use an asset pipeline tool to take a deep control over your configuration.

You can consider to use WUIC and extend it according to your need.

You can use the maven-plugin, enable YUICompressor support and then just write a custom ObjectBuilderInspector that will specify to the aggregator your custom Transformer that wraps your content.

Please find some piece of code bellow, you will find the documentation here and the samples here and here.

pom.xml

<build>
    <plugins>
        <plugin>
            <groupId>com.github.wuic.plugins</groupId>
            <artifactId>static-helper-maven-plugin</artifactId>
            <version>${project.version}</version>
            <executions>
                <execution>
                    <phase>generate-resources</phase>
                    <goals>
                        <goal>process</goal>
                    </goals>
                </execution>
            </executions>
            <configuration>
                <xml>src/main/resources/wuic.xml</xml>
                <properties>src/main/resources/wuic.properties</properties>
                <output>${project.build.finalName}</output>
            </configuration>
            <dependencies>
                <dependency>
                    <groupId>com.github.wuic.extensions</groupId>
                    <artifactId>wuic-yuicompressor</artifactId>
                    <version>${project.version}</version>
                </dependency>
            </dependencies>
        </plugin>
    </plugins>
</build>

wuic.xml:

<wuic>
    <heaps>
        <heap id="scripts">
            <nut-path>*/lib/*</nut-path>
            <nut-path>*/*-min.js</nut-path>
            <nut-path>*/*.min.js</nut-path>
            <nut-path>*/*-min.css</nut-path>
            <nut-path>*/*.min.css</nut-path>
        </heap>
    </heaps>
</wuic>

wuic.properties

# for resources in classpath (src/main/resources)
c.g.wuic.dao.wildcard=true
c.g.wuic.dao.basePath=/js/app
c.g.wuic.facade.additionalBuilderInspectorClasses=com.your.app.MyInspector

Your custom transformer that is plugged thanks to an inspector

public class MyInspector implements ObjectBuilderInspector, Pipe.Transformer<ConvertibleNut> {

        @Override
    public <T> T inspect(T object) {
        if (object instanceof TextAggregatorEngine) {
            TextAggregatorEngine.class.cast(object).addTransformer(this);
        }

        return object;
    }

    @Override
    public void transform(InputStream is, OutputStream os, ConvertibleNut convertible) throws IOException {
        if (convertible.getNutType().equals(NutType.JAVASCRIPT)) {
            os.write("(function(){".getBytes());
            IOUtils.copyStream(is, os);
            os.write("})();".getBytes());
        } else {
            IOUtils.copyStream(is, os);
        }
    }

    @Override
    public boolean canAggregateTransformedStream() {
        return false;
    }
}