How do I build the android obb file from the command line

I can create the apk with the following: Engine/Binaries/DotNET/UnrealBuildTool.exe projectname Android DebugGame -p /path/to/projectname.uproject and install it but it won’t work until I have packaged and installed or launched the game from the editor first. How do I build the obb file without using the gui/editor?