testReportDirectory cannot be changed

<plugin>
    <groupId>de.saumya.mojo</groupId>
    <artifactId>rspec-maven-plugin</artifactId>
    <version>1.1.5</version>
    <extensions>true</extensions>
    <configuration>
        <testReportDirectory>${project.build.directory}</testReportDirectory>
    </configuration>
    <executions>
        <execution>
            <phase>test</phase>
            <goals>
                <goal>test</goal>
            </goals>
        </execution>
    </executions>
</plugin>

I've tried relative and absolute paths, but reports always end up in ${project.build.directory}/surefire-reports.

The reason I want to reconfigure this is because Jenkins looks for the test results in target/surefire-reports and I want to use the rspec_junit_formatter but I haven't found a way to specify the formatter I want rspec-maven-plugin to use so I add it to rspec.args like this:

mvn clean install -Drspec.args="--format RspecJunitFormatter --out target/surefire-reports/TEST-rspec-junit.xml ./src/test/ruby/"