Use jacoco plugin through direct invocation instead of as report to avoid running extra site reports that are not needed.

Change-Id: I35c44d1a5748a4318bd0736e057839b633473a3b
diff --git a/releng/jacoco-report/pom.xml b/releng/jacoco-report/pom.xml
index 7874c52..7393a32 100644
--- a/releng/jacoco-report/pom.xml
+++ b/releng/jacoco-report/pom.xml
@@ -150,25 +150,23 @@
         <configuration>
           <skip>false</skip>
           <skipDeploy>false</skipDeploy>
-          <generateReports>true</generateReports>
+          <generateReports>false</generateReports>
         </configuration>
       </plugin>
-    </plugins>
-  </build>
-
-  <reporting>
-    <plugins>
       <plugin>
-        <groupId>org.jacoco</groupId>
-        <artifactId>jacoco-maven-plugin</artifactId>
-        <reportSets>
-          <reportSet>
-            <reports>
-              <report>report-aggregate</report>
-            </reports>
-          </reportSet>
-        </reportSets>
-      </plugin>
-    </plugins>
-  </reporting>
+       <groupId>org.jacoco</groupId>
+       <artifactId>jacoco-maven-plugin</artifactId>
+       <executions>
+         <execution>
+           <id>generate-aggregate-jacoco-report</id>
+           <inherited>false</inherited>
+           <phase>pre-site</phase>
+           <goals>
+             <goal>report-aggregate</goal>
+           </goals>
+         </execution>
+       </executions>
+     </plugin>
+   </plugins>
+ </build>
 </project>
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