Flutter - Packages are not supported when using legacy build locations, but the current project has them enabled.

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 Legacy to Xcode default.

Also open the Runner.xcodeproj, go to File->Project Settings->Per-User Project Settings->Advanced and change from Legacy to Xcode default.

It's done. Try again run flutter build ios and see it works for you.