Flutter generate android & iOS build.

build.txt

  Creating the Android build.
  
  1)Go to your project root folder (open terminal that path.)
  2)Run flutter build --release you can remove release if you want.
  then you will find your apk in Project root->build->app->outputs->flutter-apk->your apk.
  
  Creating IOS build.
  
  1)Go to your project root folder (open terminal that path.)
  2)Run flutter build ios.
  3)After the above command is successful you get the runner path in your terminal.
    Generally it will be project root->build->ios->iphoneos
  4)Here you will find your runner file.
  5)Create a new folder in the same directory with the Payload name. (Case-sensitive)
  6)Move your runner file to the Payload folder to compress it.
  7)Change the extension to zip to IPA.