The app doesn't support that, but there is a workaround.
1: Select "Build universal APK" when you build the app.
2: Wait until it prompts to install the app, and then click cancel.
3: Click "Share" and send the file to yourself.
4: Rename the file from "file.apks" to "file.zip"
5: Unzip the file, and you will find the APK file inside