Qt apps cannot be built against an SDK with extensions

Building my Qt 6.4 app (6.4.2 from the installer) for Android on the GitHub CI suddenly started failing with

Starting a Gradle Daemon (subsequent builds will be faster)
FAILURE: Build completed with 2 failures.

    1: Task failed with an exception.
    -----------
    * Where:
    Build file '/home/runner/work/brickstore/brickstore/build/android-build/build.gradle' line: 37

    * What went wrong:
    A problem occurred evaluating root project 'android-build'.
    > For input string: "ext4" 

My build.gradle is fairly Qt standard and line 37 reads:

compileSdkVersion androidCompileSdkVersion.toInteger() 

Googling for "ext4", I found that Android SDK now come with extensions and version 33 is currently at "extension level 4". Sure enough the GitHub runners have been updated to android-33-ext4 and our androiddeployqt cannot handle this. It creates the gradle.properties file like this:

 gradleProperties["androidCompileSdkVersion"] = options.androidPlatform.split(u'-').last().toLocal8Bit();
 

which chops off the "ext4" from "android-33-ext4" and puts it into the sdk version, which of course is neither the SDK version, nor can it be run through toInteger().

I think we should switch from last() to at(1) to make it possible to build Qt apps again, but then we should also make sure to get the extension level across to build.gradle as compileSdkExtension 4, but this would require updated templates in every app.

(see https://developer.android.com/guide/sdk-extensions for more information)