Generating with maven-exec

pom.xml

<plugin>
  <groupId>org.codehaus.mojo</groupId>
  <artifactId>exec-maven-plugin</artifactId>
  <version>1.2.1</version>
  <executions>
    <execution>
      <id>mwe2Launcher</id>
      <phase>generate-sources</phase>
      <goals>
        <goal>java</goal>
      </goals>
    </execution>
  </executions>
  <configuration>
    <mainClass>org.eclipse.emf.mwe2.launch.runtime.Mwe2Launcher</mainClass>
    <arguments>
      <argument>/${project.basedir}/src/org/xtext/builddsl/GenerateBuildDSL.mwe2</argument>
    </arguments>
    <includePluginDependencies>true</includePluginDependencies>
  </configuration>
  <dependencies>
    <dependency>
      <groupId>org.eclipse.xtext</groupId>
      <artifactId>org.eclipse.xtext.xtext</artifactId>
      <version>${xtext-version}</version>
    </dependency>
    <dependency>
      <groupId>org.eclipse.xtext</groupId>
      <artifactId>org.eclipse.xtext.xbase</artifactId>
      <version>${xtext-version}</version>
    </dependency>
  </dependencies>
</plugin>