title: Flutter error: Unable to locate gradlew script
body: <p>I can't run all of my flutter apps, because in the console appears everytime this error message:</p>
  <pre><code>Downloading Gradle Wrapper...                                       1,2s
  Launching lib\main.dart on SM G960F in debug mode...
  Running Gradle task 'assembleDebug'...
  Finished with error: Unable to locate gradlew script. Please check that C:\Users\...\android\gradlew.bat exists or that C:\Users\...\android can be read.
  </code></pre>
  <p>I try to fix this problem more than ten hours and don't find a solution.</p>