Install/load QPlatformInputContextPlugin on Android

[KroMignon]

I have create a simple on screen keyboard plugin and I want to use it with an Android project.

In my project, there a many sub-projects (custom libs, application, plugins).
For the share libs, I only had to ANDROID_EXTRA_LIBS to ensure they are in the APK. This works fine.

But for the Keyboard plugin, be loadable by Qt, the plugin must be in a sub-directory "platforminputcontexts" (according http://doc.qt.io/qt-5/plugins-howto.html). I don't know how to do that.
Is there another environment variable I have to set?

Thanks for any help.