archetype の packaging が maven-plugin のままだと以下の警告がでます。

[WARNING] *******************************************************
[WARNING] Deprecation Alert:
[WARNING] No mojo descriptors were found in this project which has a packaging type of maven-plugin.
[WARNING] In future versions of the plugin tools, this will fail the build.
[WARNING] If this project is an archetype, change the packaging type from maven-plugin to maven-archetype.
[WARNING] ********************************************************

packaging を maven-archetype に変更します。