title: Flutter/ fatal error: 'Flutter/Flutter.h' file not found
body: <p>Hello i am having this error when I run my app.</p>
  <pre><code>Failed to build iOS app
  Error output from Xcode build:
  ↳
      ** BUILD FAILED **
  Xcode's output:
  ↳
      In file included from /Users/daegilpyo/Developer/flutter/.pub-cache/hosted/pub.dartlang.org/url_launcher-5.7.10/ios/Classes/FLTURLLauncherPlugin.m:7:
      /Users/daegilpyo/Developer/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.
  5
      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.
  
  Error launching application on DAEGIL의 iPhone.
  Exited (sigterm)
  </code></pre>
  <p>This is happening after I change the channel from stable to master..
  I don`t know why I am having this error.</p>
  <p>Plz let me know, I am waiting for you help..</p>
  <p>this is flutter doctor - v</p>
  <pre><code>[✓] Flutter (Channel stable, 1.22.5, on macOS 11.0.1 20B50 darwin-x64, locale en-CA)
      • Flutter version 1.22.5 at /Users/daegilpyo/Developer/flutter
      • Framework revision 7891006299 (5 days ago), 2020-12-10 11:54:40 -0800
      • Engine revision ae90085a84
      • Dart version 2.10.4
  
  [✓] Android toolchain - develop for Android devices (Android SDK version 29.0.3)
      • Android SDK at /Users/daegilpyo/Library/Android/sdk
      • Platform android-29, build-tools 29.0.3
      • Java binary at: /Applications/12.app/Contents/jre/jdk/Contents/Home/bin/java
      • Java version OpenJDK Runtime Environment (build 1.8.0_212-release-1586-b4-5784211)
      • All Android licenses accepted.
  
  [✓] Xcode - develop for iOS and macOS (Xcode 12.2)
      • Xcode at /Applications/Xcode.app/Contents/Developer
      • Xcode 12.2, Build version 12B45b
      • CocoaPods version 1.10.0
  
  [✓] Android Studio (version 3.6)
      • Android Studio at /Applications/12.app/Contents
      • Flutter plugin version 47.1.1
      • Dart plugin version 192.8052
      • Java version OpenJDK Runtime Environment (build 1.8.0_212-release-1586-b4-5784211)
  
  [✓] Connected device (1 available)
      • DAEGIL의 iPhone (mobile) • 00008020-0011243A2279002E • ios • iOS 14.2
  
  • No issues found!
  </code></pre>