using gem-maven-plugin to compass compile

pom.xml

<?xml version="1.0"?>
<project
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
    xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.example</groupId>
  <artifactId>example</artifactId>
  <version>0.0.36</version>

  <repositories>
    <repository>
      <id>rubygems-releases</id>
      <url>http://rubygems-proxy.torquebox.org/releases</url>
    </repository>
  </repositories>

  <dependencies>
    <dependency>
      <groupId>rubygems</groupId>
      <artifactId>compass</artifactId>
      <version>0.11.7</version>
      <type>gem</type>
    </dependency>
  </dependencies>
  <build>
    <plugins>
      <plugin>
        <groupId>de.saumya.mojo</groupId>
        <artifactId>gem-maven-plugin</artifactId>
        <version>0.28.6</version>
	<extensions>true</extensions>
        <executions>
	  <execution>
	    <goals>
	      <goal>exec</goal>
	    </goals>
	    <phase>compile</phase>
	  </execution>
	</executions>
	<configuration>
	  <!--jrubyVersion>1.6.4</jrubyVersion-->
	  <execArgs>${project.build.directory}/rubygems/bin/compass compile ${basedir}/src/main/sass</execArgs>
	</configuration>
      </plugin>
    </plugins>
  </build>
</project>