title: Flutter iOS build failure error with Multiple commands after the Xcode upgrade
body: <p>Flutter iOS build fails after upgrading to Xcode 10.0 version in mac.</p>
  <pre><code>Nagendras-MacBook-Pro:uaenumber nagendra$ flutter run
  Launching lib/main.dart on iPhone X in debug mode...
  Starting Xcode build...
  Xcode build done.                                            1.4s
  Failed to build iOS app
  Error output from Xcode build:
  ↳
      ** BUILD FAILED **
  
  Xcode's output:
  ↳
      error: Multiple commands produce '/Users/dev/Documents/projects/Personal/uaenumber/build/ios/Debug-iphonesimulator/Runner.app/Frameworks/Flutter.framework':
      1) Target 'Runner' has copy command from '/Users/dev/Documents/projects/Personal/uaenumber/ios/Flutter/Flutter.framework' to '/Users/dev/Documents/projects/Personal/uaenumber/build/ios/Debug-iphonesimulator/Runner.app/Frameworks/Flutter.framework'
      2) That command depends on command in Target 'Runner': script phase “[CP] Embed Pods Frameworks”
      warning: The use of Swift 3 @objc inference in Swift 4 mode is deprecated. Please address deprecated @objc inference warnings, test your code with “Use of deprecated Swift 3 @objcinference” logging enabled, and then disable inference by changing the &quot;Swift 3 @objc Inference&quot; build setting to &quot;Default&quot; for the &quot;Runner&quot; target. (in target 'Runner')
      warning: ignoring duplicated output file: '/Users/nagendra/Documents/projects/Personal/uaedialer/build/ios/Debug-iphonesimulator/Runner.app/Frameworks/Flutter.framework' (in target 'Runner')
      note: Using new build systemnote: Planning buildnote: Constructing build description
  Could not build the application for the simulator.
  Error launching application on iPhone X.
  </code></pre>
  <p>Xcode Version - 10.0 (10A255)</p>
  <p>I tried to recreate the project and copied all the source files to the new project folder but it does not resolve the issue.</p>