Move buildSrc classes to androidx.build package.

Test: ./gradlew assembleDebug for support and flatfoot projects
Change-Id: I9ecada2082209e46058dbce453d7222d3999c925
diff --git a/buildSrc/init.gradle b/buildSrc/init.gradle
index 38b41e8bc..4faeac5 100644
--- a/buildSrc/init.gradle
+++ b/buildSrc/init.gradle
@@ -15,9 +15,9 @@
  */
 
 
-import android.support.DiffAndDocs
-import android.support.gmaven.GMavenVersionChecker
-import android.support.license.CheckExternalDependencyLicensesTask
+import androidx.build.DiffAndDocs
+import androidx.build.gmaven.GMavenVersionChecker
+import androidx.build.license.CheckExternalDependencyLicensesTask
 import com.android.build.gradle.internal.coverage.JacocoReportTask
 import com.android.build.gradle.internal.tasks.DeviceProviderInstrumentTestTask
 import org.gradle.api.logging.configuration.ShowStacktrace