M2_HOME は削除されました。 MNGSITE-283 Remove M2_HOME from documentation MNG-5607 Don’t use M2_HOME in mvn shell/command scripts anymore 3.5.0 リリースノート “Based on problems in using M2_HOME related to different Maven versions installed and to simplify things, the usage of M2_HOME has been removed and is not supported any more MNG-5823, MNG-5836, MNG-5607.” (変更 commit) 敢え