title: Enabling androidX causes 'Cannot change strategy of configuration ':app:compile' after it has been resolved' error
body: <p>I am currently trying to migrate OpenId/Android-Apputh to androidX and facing a strange problem after performing all changes gradle starts throwing the following error :</p>
  
  <pre><code>&gt; Cannot change strategy of configuration ':app:compile' after it has been resolved.
  </code></pre>
  
  <p>After I add </p>
  
  <pre><code>android.enableJetifier=true
  android.useAndroidX=true
  </code></pre>
  
  <p>to 'gradle.properties'</p>
  
  <p><strong>Hint</strong></p>
  
  <p>I tried to log all possible (using <code>println(cofigBlockName)</code>) configuration blocks and found that <code>sourceSets</code> configBlock was not called during the build process. So it could be that Jetifier applies some settings to <code>sourceSets</code>.</p>
  
  <p>Does anybody know how to fix that?</p>
  
  <p><strong>android-common.gradle</strong></p>
  
  <pre><code>android {
      compileSdkVersion rootProject.compileSdkVersion
      buildToolsVersion rootProject.buildToolsVersion
      defaultConfig {
          minSdkVersion rootProject.minSdkVersion
          targetSdkVersion rootProject.compileSdkVersion
          versionCode rootProject.versionNum
          versionName rootProject.versionName
      }
      sourceSets {
          main.manifest.srcFile 'AndroidManifest.xml'
          main.java.srcDirs = ['java']
          main.aidl.srcDirs = ['java']
          main.res.srcDir 'res'
          main.assets.srcDir 'assets'
          main.resources.srcDir 'java'
          test.setRoot('javatests');
          test.java.srcDir('javatests');
      }
      compileOptions {
          sourceCompatibility JavaVersion.VERSION_1_8
          targetCompatibility JavaVersion.VERSION_1_8
      }
      lintOptions {
          warningsAsErrors true
          disable 'InvalidPackage', 'TrulyRandom', 'UseCompoundDrawables', 'GradleDependency'
      }
      packagingOptions {
          exclude 'META-INF/LICENSE.txt'
          exclude 'META-INF/NOTICE.txt'
      }
  }
  
  // produces just the classes JAR
  task jar(type: Copy, dependsOn:'bundleRelease') {
      from("${project.buildDir}/intermediates/bundles/release/")
      into("${project.buildDir}/libs/")
      include('classes.jar')
      rename('classes.jar', "appauth-${rootProject.versionName}.jar")
  }
  
  // produces a JAR containing sources
  task sourcesJar(type: Jar, dependsOn:'generateReleaseSources') {
      from android.sourceSets.main.java.srcDirs
      classifier = 'sources'
  }
  
  tasks.withType(JavaCompile) {
      options.compilerArgs &lt;&lt; "-Xlint:deprecation" &lt;&lt; "-Xlint:unchecked"
  }
  </code></pre>
  
  <p><strong>build.gradle</strong></p>
  
  <pre><code>apply plugin: 'com.android.application'
  apply plugin: 'checkstyle'
  apply from: '../config/android-common.gradle'
  apply from: '../config/keystore.gradle'
  
  android {
      defaultConfig {
          applicationId 'net.openid.appauthdemo'
          project.archivesBaseName = 'appauth-demoapp'
          vectorDrawables.useSupportLibrary = true
  
          // Make sure this is consistent with the redirect URI used in res/raw/auth_config.json,
          // or specify additional redirect URIs in AndroidManifest.xml
          manifestPlaceholders = [
                  'appAuthRedirectScheme': 'com.lohika.android.test'
          ]
      }
  
      signingConfigs {
          debugAndRelease {
              storeFile file("${rootDir}/appauth.keystore")
              storePassword "appauth"
              keyAlias "appauth"
              keyPassword "appauth"
          }
      }
  
      compileOptions {
          sourceCompatibility JavaVersion.VERSION_1_8
          targetCompatibility JavaVersion.VERSION_1_8
      }
  
      buildTypes {
          debug {
              signingConfig signingConfigs.debugAndRelease
          }
          release {
              signingConfig signingConfigs.debugAndRelease
          }
      }
  }
  
  project.ext.glideVersion = '4.7.1'
  
  dependencies {
      implementation fileTree(dir: 'libs', include: ['*.jar'])
      implementation project(':library')
      implementation 'androidx.appcompat:appcompat:1.1.0-alpha01'
      implementation 'com.google.android.material:material:1.1.0-alpha02'
      implementation "com.github.bumptech.glide:glide:${project.glideVersion}"
      implementation 'com.squareup.okio:okio:1.14.1'
      implementation 'joda-time:joda-time:2.10'
  
      annotationProcessor "com.github.bumptech.glide:compiler:${project.glideVersion}"
  }
  
  apply from: '../config/style.gradle'
  </code></pre>