title: Task 'assembleRelease' not found in root project 'android'
body: <p>I'm using <strong>Reactnative 0.54.0</strong> and <strong>react-native-cli 2.0.1</strong> along side <strong>gradle 4.8.1</strong></p>
  
  <p>I have created a react-native project using <strong>create-react-native-app myProjectName</strong></p>
  
  <p>When I created the project, it doesn't include android and ios folders, so I added them manually.</p>
  
  <p>I also installed gradle using <strong>choco</strong> and then created a wrapper for it using <strong>gradle wrapper --gradle-version 4.8.1 --distribution-type all</strong></p>
  
  <p>so I am developing react-native using microsoft <strong>vsCode</strong> and then see my application in action using <strong>Genymotion</strong> emulator, everything is fine</p>
  
  <p>now, I want to generate the final <strong>Signed APK</strong> for play store, I'm using this guide provided by react-native </p>
  
  <p><a href="https://facebook.github.io/react-native/docs/signed-apk-android.html" rel="noreferrer">https://facebook.github.io/react-native/docs/signed-apk-android.html</a></p>
  
  <p>When I want to run <strong>gradlew assembleRelease</strong> I get this error</p>
  
  <pre><code>C:\myApp\android&gt;gradlew assembleRelease
  
  FAILURE: Build failed with an exception.
  
  * What went wrong:
  Task 'assembleRelease' not found in root project 'android'.
  
  * Try:
  Run gradlew tasks to get a list of available tasks. Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.
  
  * Get more help at https://help.gradle.org
  
  BUILD FAILED in 4s
  </code></pre>
  
  <p>what's wrong with assembleRelease? what should I do?</p>
  
  <p>to add more info, I have to say that when I want to build this project in VSTS (TFS Online) I get this error</p>
  
  <pre><code>2018-07-17T16:20:14.9268702Z ##[error]Error: Not found wrapperScript: D:\a\1\s\gradlew
  </code></pre>
  
  <p>Any clue is appriciated
  Thanks</p>
  
  <p><strong>Update:</strong>
  as @philipp asked, this is the list of tasks that gradlew have listed and assembleRelease is not one one them!!!! what's the reason?</p>
  
  <pre><code>C:\myApp\Android&gt;gradlew tasks
  
  &gt; Task :tasks
  
  ------------------------------------------------------------
  All tasks runnable from root project
  ------------------------------------------------------------
  
  Build Setup tasks
  -----------------
  init - Initializes a new Gradle build.
  wrapper - Generates Gradle wrapper files.
  
  Help tasks
  ----------
  buildEnvironment - Displays all buildscript dependencies declared in root project 'android'.
  components - Displays the components produced by root project 'android'. [incubating]
  dependencies - Displays all dependencies declared in root project 'android'.
  dependencyInsight - Displays the insight into a specific dependency in root project 'android'.
  dependentComponents - Displays the dependent components of components in root project 'android'. [incubating]
  help - Displays a help message.
  model - Displays the configuration model of root project 'android'. [incubating]
  projects - Displays the sub-projects of root project 'android'.
  properties - Displays the properties of root project 'android'.
  tasks - Displays the tasks runnable from root project 'android'.
  
  To see all tasks and more detail, run gradlew tasks --all
  
  To see more detail about a task, run gradlew help --task &lt;task&gt;
  
  BUILD SUCCESSFUL in 1s
  1 actionable task: 1 executed
  </code></pre>
  
  <p>and this is myApp\android**build.gradle**</p>
  
  <pre><code>project.ext.react = [
      bundleInStaging: true 
  ]
  task wrapper(type: Wrapper) {
      gradleVersion = '4.8.1'
  }
  android {
      defaultConfig {
          applicationId "com.sunkime.client"
      }
      signingConfigs {
          staging {
              keyAlias = "staging"
              storeFile = file("my-release-key.keystore")
              keyPassword = "qwert%$#@!"
              storePassword = "qwert%$#@!"
          }
          release {
              if (project.hasProperty('MYAPP_RELEASE_STORE_FILE')) {
                  storeFile file(MYAPP_RELEASE_STORE_FILE)
                  storePassword qwert%$#@!
                  keyAlias qwert%$#@!
                  keyPassword qwert%$#@!
              }
          }
      }
      buildTypes {
          debug {
              applicationIdSuffix ".debug"
          }
          staging {
              applicationIdSuffix ".staging"
              signingConfig signingConfigs.staging
              minifyEnabled true
              proguardFiles getDefaultProguardFile("proguard-android.txt"), "proguard-rules.pro"
          }
  
          release {
              applicationIdSuffix ".release"
              signingConfig signingConfigs.release
              minifyEnabled true
              proguardFiles getDefaultProguardFile("proguard-android.txt"), "proguard-rules.pro"
          }
      }
  }
  </code></pre>
  
  <p>I also used <strong>gradlew clean</strong> and no difference</p>