or {@code combine.self} attributes to the children of the configuration element:</p>
            <ul>
            <li>{@code combine.children}: available values are {@code merge} (default) and {@code append},</li>
            <li>{@code combine.self}: available values are {@code merge} (default) and {@code override}.</li>
            </ul>

            <artifactId>maven-compiler-plugin</artifactId>
            <configuration>
              <!-- Under JDK8, we continue to use errorprone's javac9 (even
                   though we don't run Error Prone itself, which no longer
                   supports JDK8!).

                   Why? At some point, presumably after
                   https://github.com/google/guava/commit/e06a8cec65815599e510d7f9c1ea9d2a8eaa438a,