By default, the repackage goal will replace the original artifact with the executable one. If you prefer to keep the original artifact and attach the executable one with a different classifier, configure the plugin as follows:

<project>
  ...
  <build>
    ...
    <plugins>
      ...
      <plugin>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-maven-plugin</artifactId>
        <version>1.3.8.RELEASE</version>
        <executions>
          <execution>
            <goals>
              <goal>repackage</goal>
            </goals>
            <configuration>
              <classifier>exec</classifier>
            </configuration>
          </execution>
        </executions>
        ...
      </plugin>
      ...
    </plugins>
    ...
  </build>
  ...
</project>

This configuration will generate two artifacts: the original one and the executable counter part produced by the repackage goal. Both will be installed/deployed accordingly.