title: Ionic build ios does not work with xcode 8 beta
body: <p>I recently downloaded the Xcode 8 beta and replaced it in applications. Now when I execute "ionic build ios" I get this error:</p>
  
  <pre><code>xcode-select: error: tool 'xcodebuild' requires Xcode, but active developer directory '/Library/Developer/CommandLineTools' is a command line tools instance
  ERROR building one of the platforms: Error: ***/platforms/ios/cordova/build: Command failed with exit code 2
  You may not have the required environment or OS to build this project
  Error: ***/platforms/ios/cordova/build: Command failed with exit code 2
      at ChildProcess.whenDone (/usr/local/lib/node_modules/cordova/node_modules/cordova-lib/src/cordova/superspawn.js:139:23)
      at emitTwo (events.js:87:13)
      at ChildProcess.emit (events.js:172:7)
      at maybeClose (internal/child_process.js:818:16)
      at Process.ChildProcess._handle.onexit (internal/child_process.js:211:5)
  </code></pre>
  
  <p>I already tried:</p>
  
  <p>1) ionic platform rm ios
  2) ionic platform add ios</p>
  
  <p>Would appreciate some advice. Thanks!</p>