You can use the outputDirectory parameter of the maven-jar-plugin for this purpose:
<project>
...
<build>
<plugins>
...
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>2.3.1</version>
<configuration>
<outputDirectory>../libs</outputDirectory>
</configuration>
</plugin>
...
</plugins>
</build>
...
</project>
But as cdegroot wrote, you should probably better not fight the maven way.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…