Maven complete setup for build

Hi, I'm setting up a build environment, a simple linux. I have experience with build environment and maven.

I try to setup a build environment instead of building final IAR from designer. I've ask a few question already: http://answers.axonivy.com/questions/2279/is-there-an-axon-ivy-repository-for-maven
http://answers.axonivy.com/questions/2219/504-gateway-time-out-on-guidelines-axonivy-com-projects-guides-wiki-continues_integration

• I've read the thin document on Maven plugin: https://axonivy.github.io/project-build-plugin/release/6.4/index.html
• Continuous integration here: http://developer.axonivy.com/doc/latest/DesignerGuideHtml/ivy.concepts.html#ivy-ci
• I've try (and failed) to launch example projects: https://github.com/axonivy/project-build-examples/tree/master

I have several idea what I need to do to get these work, but instead or forging a custom solution I would like to used a recommended one. Last thing I've try the ensureInstalledEngine was trying to download the windows version of AxonIvyEngine on my build machine. I can install the engine, is it necessary? do I need to install multiple engine to build project of multiple version? We want to get things right because this application is deploy, we have several clients on our solutions and we need to support them and do maintenance. We have to deploy new version and we want to be sure what we are doing (hence setup a controlled build environment) and avoid interference between project (like we experience in Designer).

[INFO] --- project-build-plugin:6.0.0:ensureInstalledEngine (default-ensureInstalledEngine) @ MyProject ---  
[INFO] Compiling project for ivy version 6.0.0  
[INFO] Installed engine has version 'null' instead of expected '6.0.0'  
[INFO] Starting engine download from http://download.axonivy.com/6.0.0/AxonIvyEngine6.0.0.50515_Windows_x64.zip

Thanks!