title: fatal error: 'Flutter/Flutter.h' file not found when running for iOS
body: <p>I have a flutter app which was using only the android side. Now I want to run it on a iPad but it throws this error:</p>
  <pre><code>Error output from Xcode build:
  ↳
      2021-04-19 11:31:26.233 xcodebuild[21793:154600]  DVTAssertions: Warning in /Library/Caches/com.apple.xbs/Sources/DVTiOSFrameworks/DVTiOSFrameworks-17705/DTDeviceKitBase/DTDKRemoteDeviceData.m:371
      Details:  (null) deviceType from 00008101-00126D441E38001E was NULL when -platform called.
      Object:   &lt;DTDKMobileDeviceToken: 0x7f8196cb0f70&gt;
      Method:   -platform
      Thread:   &lt;NSThread: 0x7f8196c6dc80&gt;{number = 8, name = (null)}
      Please file a bug at https://feedbackassistant.apple.com with this warning message and any useful information you can provide.
      2021-04-19 11:31:26.651 xcodebuild[21793:154569]  DVTAssertions: Warning in /Library/Caches/com.apple.xbs/Sources/DVTiOSFrameworks/DVTiOSFrameworks-17705/DTDeviceKitBase/DTDKRemoteDeviceData.m:371
      Details:  (null) deviceType from 00008101-00126D441E38001E was NULL when -platform called.
      Object:   &lt;DTDKMobileDeviceToken: 0x7f8196cb0f70&gt;
      Method:   -platform
      Thread:   &lt;NSThread: 0x7f8196a38370&gt;{number = 5, name = (null)}
      Please file a bug at https://feedbackassistant.apple.com with this warning message and any useful information you can provide.
      2021-04-19 11:31:26.835 xcodebuild[21793:154569]  DVTAssertions: Warning in /Library/Caches/com.apple.xbs/Sources/DVTiOSFrameworks/DVTiOSFrameworks-17705/DTDeviceKitBase/DTDKRemoteDeviceData.m:371
      Details:  (null) deviceType from 00008101-00126D441E38001E was NULL when -platform called.
      Object:   &lt;DTDKMobileDeviceToken: 0x7f8196cb0f70&gt;
      Method:   -platform
      Thread:   &lt;NSThread: 0x7f8196a38370&gt;{number = 5, name = (null)}
      Please file a bug at https://feedbackassistant.apple.com with this warning message and any useful information you can provide.
      ** BUILD FAILED **
  
  
  Xcode's output:
  ↳
      In file included from /Users/interno/Documents/FlutterSDK/flutter/.pub-cache/hosted/pub.dartlang.org/url_launcher-5.7.10/ios/Classes/FLTURLLauncherPlugin.m:7:
      /Users/interno/Documents/FlutterSDK/flutter/.pub-cache/hosted/pub.dartlang.org/url_launcher-5.7.10/ios/Classes/FLTURLLauncherPlugin.h:5:9: fatal error: 'Flutter/Flutter.h' file not found
      #import &lt;Flutter/Flutter.h&gt;
              ^~~~~~~~~~~~~~~~~~~
      1 error generated.
      Command CompileSwift failed with a nonzero exit code
      Command CompileSwift failed with a nonzero exit code
      note: Using new build system
      note: Building targets in parallel
      note: Planning build
      note: Constructing build description
  
  Could not build the precompiled application for the device.
  
  </code></pre>
  <p>Things I already tried:</p>
  <ul>
  <li>Run flutter clean</li>
  <li>pod install</li>
  <li>pod update</li>
  <li>Delete the 'iOS' folder and run 'flutter create'</li>
  </ul>
  <p>What I have to do to fix it?</p>