Delete certain proguard rule

proguard-aftertask.gradle

```groovy
afterEvaluate {
  // All proguard tasks shall depend on our filter task
  def proguardTasks = tasks.findAll { task ->
    task.name.startsWith('transformClassesAndResourcesWithProguardFor') }
  proguardTasks.each { task -> task.dependsOn filterConsumerRules }
}

// Let define our custom task that filters some unwanted
// consumer proguard rules
task(filterConsumerRules) << {
  // Collect all consumer rules first
  FileTree allConsumerRules = fileTree(dir: 'build/intermediates/exploded-aar', include: '**/proguard.txt')

  // Now filter the ones we want to exclude:
  // Change it to fit your needs, replace library with
  // the name of the aar you want to filter.
  FileTree excludeRules = allConsumerRules.matching {
    include '**/library/**'
  }

  // Print some info and delete the file, so ProGuard
  // does not pick it up. We could also just rename it.
  excludeRules.each { File file ->
    println 'Deleting ProGuard consumer rule ' + file
    file.delete()
  }
}

```