Which version of Project build pluggin for Ivy Engine 6.1.0

You can configure the ivy version which is used by the project-build-plugin. It currently defaults to 6.0.1, but you can always change it by settings the parameter ivyVersion. See the goal documentation here http://axonivy.github.io/project-build-plugin/release/ensureInstalledEngine-mojo.html#ivyVersion

<build>
    <plugins>
      <plugin>
        <groupId>com.axonivy.ivy.ci</groupId>
        <artifactId>project-build-plugin</artifactId>
        <version>6.0.3</version>
        <extensions>true</extensions>
        <configuration>
            <ivyVersion>6.0.2</ivyVersion>
        </configuration>
      </plugin>
    </plugins>
  </build>

If you compile a project for a 6.1 engine i suggest that you migrate to the latest project-build-plugin which is built for 6.1. As 6.1 is not yet released and only availalbe as sprint increment, the corresponding plugin is also only available in as SNAPSHOT release. But you can and should use it anyway as it brings many new features: http://axonivy.github.io/project-build-plugin/snapshot/plugin-info.html

<pluginRepositories>
    <!-- Snapshot releases are not deployed to maven central. So the repo on sonatype could be used instead -->
    <pluginRepository>
        <id>sonatype</id>
        <url>https://oss.sonatype.org/content/repositories/snapshots</url>
        <snapshots>
            <updatePolicy>always</updatePolicy>
        </snapshots>
    </pluginRepository>
</pluginRepositories>

<build>
        <plugins>
            <plugin>
                <groupId>com.axonivy.ivy.ci</groupId>
                <artifactId>project-build-plugin</artifactId>
                <version>6.1.0-SNAPSHOT</version>
            </plugin>
        </plugins>
</build>