Replace main/android-mkdtboimg with Alpine's community/android-tools

As per https://pkgs.alpinelinux.org/contents?branch=edge&name=android-tools&arch=x86_64&repo=community android-tools now has mkdtboimg which could be used to replace the android-mkdtboimg package (which installs both mkdtimg and mkdtboimg.py executables).

Essentially it is the exact same Python script but updated along with everything else on https://github.com/nmeum/android-tools.