maven-archetype-archetype/src/main/resources/archetype-resources/pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>${groupId}</groupId>
  <artifactId>${artifactId}</artifactId>
  <version>${version}</version>
  <packaging>maven-archetype</packaging>

  <name>Archetype - ${artifactId}</name>

  <!-- FIXME change it to the project's website -->
  <url>http://www.example.com</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <build>
    <extensions>
      <extension>
        <groupId>org.apache.maven.archetype</groupId>
        <artifactId>archetype-packaging</artifactId>
        <version>2.2</version>
      </extension>
    </extensions>
    <pluginManagement>
      <plugins>
        <plugin>
          <artifactId>maven-archetype-plugin</artifactId>
          <version>2.2</version>
          <extensions>true</extensions>
        </plugin>
      </plugins>
    </pluginManagement>
  </build>
</project>