according to this tutorial (UE4 - recompiling plugins (Windows & Linux) - YouTube) the command should be something like this, compiling the final plugin into the [TempFolder]:
"C:\Program Files\Epic Games\UE_4.17\Engine\Build\BatchFiles\RunUAT.bat" BuildPlugin -plugin="C:\Program Files\Epic Games\UE_4.17\Engine\Plugins\[...]\YourPlugin.uplugin" -package="[TempFolder]"