When you will build a flutter application to iOS maybe you can stumble in that error message:
Packages are not supported when using legacy build locations, but the current project has them enabled.
What I did for solve that problem was change advanced settings on project.
So open the
Runner.xcworkspace, go to
File->Workspace Settings->Per-User Workspace Settings->Advanced and change from
Also open the
Runner.xcodeproj, go to
File->Project Settings->Per-User Project Settings->Advanced and change from
It's done. Try again run
flutter build ios and see it works for you.