.mvn/extensions.xml

<?xml version="1.0" encoding="UTF-8"?>
<extensions>
  <extension>
    <groupId>org.eclipse.tycho</groupId>
    <artifactId>tycho-build</artifactId>
    <!-- must be same version as in ../pom.xml -->
    <version>2.7.1</version>
  </extension>
</extensions>