title: Jetifier does not convert support dependencies
body: <p>I cloned <a href="https://github.com/google/ExoPlayer" rel="nofollow noreferrer">ExoPlayer</a> locally and added the modules to my existing project using my <code>settings.gradle</code> as described in the documentation:</p>
  
  <pre><code>gradle.ext.exoplayerRoot = 'path/to/exoplayer'
  gradle.ext.exoplayerModulePrefix = 'exoplayer-'
  apply from: new File(gradle.ext.exoplayerRoot, 'core_settings.gradle')
  </code></pre>
  
  <p>Whenever I try to build the project, I receive the following build error:</p>
  
  <blockquote>
    <p>error: package android.support.annotation does not exist</p>
  </blockquote>
  
  <p>These happen for all <code>@NonNull</code> and <code>@Nullable</code> annotations in the <strong>ExoPlayer modules</strong>.</p>
  
  <p>I created a new project in Android Studio 3.2.1, added AndroidX support in my <code>gradle.properties</code> file and updated my <code>build.gradle</code> file accordingly.</p>
  
  <p><strong>build.gradle</strong></p>
  
  <pre><code>android {
      compileSdkVersion 28
      defaultConfig {
          minSdkVersion 26
          targetSdkVersion 28
          versionCode 1
          versionName "1.0"
      }
  
      dataBinding {
          enabled = true
      }
  
      compileOptions {
          sourceCompatibility JavaVersion.VERSION_1_8
          targetCompatibility JavaVersion.VERSION_1_8
      }
  }
  
  dependencies {
      implementation fileTree(dir: 'libs', include: ['*.jar'])
  
      //ExoPlayer
      implementation project(':exoplayer-library-core')
  }
  </code></pre>
  
  <p><strong>gradle.properties</strong></p>
  
  <pre><code>org.gradle.jvmargs=-Xmx1536m
  android.databinding.enableV2=true
  android.useAndroidX=true
  android.enableJetifier=true
  </code></pre>
  
  <p>If I understand correctly, <a href="https://stackoverflow.com/questions/51680671/what-is-jetifier/52518822#52518822">Jetifier</a> should be able to resolve and convert the support dependencies to AndroidX dependencies, but this does not seem to be the case for these local modules.</p>