- app
  > references library1, library2
- library1
- library2
  > references library3
- library3

dependencies {
    implementation project(":library1")
    implementation project(":library2")
}

dependencies {
    //for debug build just use the local project
    debugImplementation project(":library1")
    debugImplementation project(":library2")
    //for release build use manually added aar in libs folder
    releaseImplementation (name: 'library1-release', ext: 'aar')
    releaseImplementation (name: 'library2-release', ext: 'aar')
    //i need to add library3 too otherwise it will not find
    //method referenced there because aar are not bundled togheter
    //by default
    releaseImplementation (name: 'library3-release', ext: 'aar')
}

//move from scripts folder to root project folder
cd "$(dirname "$BASH_SOURCE")/../../"
//assembleRelease all the aar (which enables Proguard obfuscation)
./gradlew clean assembleRelease --info &&
//copy them in the app libs folder
cp -rf library1/build/outputs/aar/library1-release.aar app/libs/library1-release.aar
cp -rf library2/build/outputs/aar/library2-release.aar app/libs/library2-release.aar
cp -rf library3/build/outputs/aar/library3-release.aar app/libs/library3-release.aar

applicationVariants.all { variant ->
    if (variant.buildType.name == "release") {
        variant.preBuildProvider.configure {
            dependsOn(buildReleaseAar)
        }
    }
}

task buildReleaseAar {
    dependsOn (
        ':library1:assembleRelease',
        ':library2:assembleRelease',
        ':library3:assembleRelease'
    )
    doLast {
        //copy the aars from build folders in app/libs folder
    }
}

configurations {
    releaseObfuscatedAar
}

dependencies {
    //other implementations libs

    //for debug build just use the local project
    debugImplementation project(":library1")
    debugImplementation project(":library2")

    releaseObfuscatedAar('library1')
    releaseObfuscatedAar('library2')
    releaseObfuscatedAar('library3')
}

//and some other task that build the aar before checking if
//dependency is present