Adopt configuration-avoidance where possible

Before this change `./gradlew help` (with native enabled)
Created immediately: 1322
Created during configuration: 1541

after this change:
Created immediately: 596
Created during configuration: 1509

To know more about configuration avoidance: https://docs.gradle.org/current/userguide/task_configuration_avoidance.html

libraries/reflect/api/build.gradle

@@ -65,7 +65,7 @@ jar {
     manifestAttributes(manifest, project, "internal")
 }
 
-task java9Jar(type: Jar) {
+tasks.register("java9Jar", Jar) {
     archiveClassifier.set("java9")
     if (includeJava9) {
         from sourceSets.java9.output