title: ERROR: Cannot add task 'clean' as a task with that name already exists
body: <p>I am facing a problem while building from Gradle. This is the error which I am facing:</p>
  
  <blockquote>
    <p>ERROR: Cannot add task 'clean' as a task with that name already exists.</p>
  </blockquote>
  
  <p>Here is my Gradle </p>
  
  <pre><code>apply plugin: 'com.android.application'android {
  compileSdkVersion 28
  buildToolsVersion "25.0.1"
  defaultConfig {
      applicationId "net.accedegh.retrofitlibrary"
      minSdkVersion 17
      targetSdkVersion 28
      versionCode 1
      versionName "1.0"
      testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
  }
  buildTypes {
      release {
          minifyEnabled false
          proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
      }
  }dependencies {
  implementation fileTree(dir: 'libs', include: ['*.jar'])
  androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
      exclude group: 'com.android.support', module: 'support-annotations'
  })
  //noinspection GradleCompatible
  implementation 'com.android.support:appcompat-v7:28.0.0'
  implementation "com.android.support:recyclerview-v7:28.0.0"
  implementation 'com.android.support:cardview-v7:28.0.0'
  implementation 'com.squareup.retrofit2:retrofit:2.1.0'
  implementation 'com.squareup.retrofit2:converter-gson:2.1.0'
  implementation 'com.squareup.picasso:picasso:2.4.0'
  implementation 'com.github.jd-alexander:LikeButton:0.2.0'
  implementation'com.github.bumptech.glide:glide:3.7.0'compile 'com.github.varunest:sparkbutton:1.0.3'
  implementation 'com.android.support:design:28.0.0'
  androidTestCompile 'junit:junit:4.12'}
  </code></pre>
  
  <p>Top-level <code>build.gradle</code> file</p>
  
  <pre><code>// Top-level build file where you can add configuration options common to all sub-projects/modules. 
  buildscript { 
      repositories { 
          jcenter() 
          google() 
      } 
  
     dependencies { 
          classpath 'com.android.tools.build:gradle:3.3.2' 
         // NOTE: Do not place your application dependencies here; they belong 
         // in the individual module build.gradle files 
     } 
  } 
  
  allprojects { 
      repositories { 
          maven { 
              url 'maven.google.com' 
              name 'Google' 
          } 
      } 
  
      task clean(type: Delete) { 
          delete rootProject.buildDir 
      } 
  }
  </code></pre>
  
  <p>Please give me the solution if anyone knows.</p>