[Interest] Android build with gradle and proguard

[maitai]

Hello,

Since Qt5.9.3, it seems it is not possible to build Android app with 
ant, so we need to use gradle (right?)

I need to run proguard when releasing the app, so after some digging I 
have added a build.gradle in my android-src directory (initially taken 
from the one automatically generated), and added something like:
     buildTypes {
       release {
         minifyEnabled true
         proguardFiles getDefaultProguardFile('proguard-android.txt'), 
'proguard-rules.pro'
       }
     }

Now build is failing with a strange error, saying basically that 
(...)\intermediates\proguard-rules\release\aapt_rules.txt is missing

I searched a lot to fix that but no way so far.

What is the correct way to invoke proguard in qt593, and alternatively 
is there a way to go back to the good old ant compilation?

Thanks for any hints
Philippe