obvious way to ensure that.

            We could consider arranging things so that only the tests we know need this would get
            the add-opens. Right now that doesn't seem worth the effort, though.
        -->
        <test.add.opens>
          --add-opens java.base/java.lang=ALL-UNNAMED
          --add-opens java.base/java.util=ALL-UNNAMED

      <plugin>
        <artifactId>maven-compiler-plugin</artifactId>
        <configuration>
          <excludes>
            <!-- Yes, we want to exclude ForceGuavaCompilation 4 times: -->
            <!-- (And we might as well exclude DummyJavadocClass 3 times (though it would be harmless to include).) -->
            <!-- 1. Don't compile it (since that requires a *non-test* dep on gwt-user. -->