Same pipeline as build_emu.sh (gogio -> apktool MANAGE_EXTERNAL_STORAGE
injection -> debug-sign) for a real phone: -arch arm64,arm (covers any
phone from the last decade; gogio accepts a comma-separated arch list)
and output cmd/pad/pad-phone.apk. Notes in the header: on Android 11+
the user must grant 'All files access' in system settings after
installing (MANAGE_EXTERNAL_STORAGE is app-restricted; the emulator AVD
had it granted, phones do not).
