Flutter build IOS on root of my flutter app does not work

The suggestion from flutter doctor -v is quite clear

✗ Xcode installation is incomplete; a full installation is necessary for iOS development.
  Download at: https://developer.apple.com/xcode/download/
  Or install Xcode via the App Store.
  Once installed, run:
    sudo xcode-select --switch /Applications/Xcode.app/Contents/Develope

You could try starting Xcode and agree when it asks to install missing components.

Id suggest you try the dev or master channel where support for Xcode 10 should have landed. Otherwise check this suggestion https://github.com/flutter/flutter/issues/20685#issuecomment-413524718

The source of my problem was that Flutter could not find the latest installed version of Xcode.

To fix it, go to Xcode->preferences->locations->set value for command Line tools.