After upgrading flutter to the latest version (3.22.1), I encountered an error when building with `--split-per-abi`:
```
[ +1 ms] FAILURE: Build failed with an exception.
[ ] * Where:
[ ] Script '/home/runar/snap/flutter/common/flutter/packages/flutter_tools/gradle/src/main/groovy/flutter.groovy' line: 1182
[ ] * What went wrong:
[ ] A problem occurred evaluating root project 'android'.
[ ] > A problem occurred configuring project ':app'.
[ ] > org.codehaus.groovy.runtime.typehandling.GroovyCastException: Cannot cast object 'null' with class 'null' to class 'int'.
Try 'java.lang.Integer' instead
```
This PR changes the type used from `ìnt` to `Integer` which is what's used in the `ABI_VERSION` map.