Updates the build to gradle 4.9 (#32087)

There are fixes to the dependency report, most importantly for us,
it still works even if `failOnVersionConflict` would fail the build.

build.gradle

@@ -596,7 +596,7 @@ if (System.properties.get("build.compare") != null) {
       }
     }
     sourceBuild {
-      gradleVersion = "4.8.1" // does not default to gradle weapper of project dir, but current version
+      gradleVersion = gradle.getGradleVersion()
       projectDir = referenceProject
       tasks = ["clean", "assemble"]
       arguments = ["-Dbuild.compare_friendly=true"]

buildSrc/src/main/groovy/com/carrotsearch/gradle/junit4/RandomizedTestingPlugin.groovy

@@ -74,7 +74,7 @@ class RandomizedTestingPlugin implements Plugin<Project> {
         // since we can't be sure if the task was ever realized, we remove both the provider and the task
         TaskProvider<Test> oldTestProvider
         try {
-            oldTestProvider = tasks.getByNameLater(Test, 'test')
+            oldTestProvider = tasks.named('test')
         } catch (UnknownTaskException unused) {
             // no test task, ok, user will use testing task on their own
             return

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.8.1-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.9-all.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionSha256Sum=ce1645ff129d11aad62dab70d63426fdce6cfd646fa309dc5dc5255dd03c7c11
+distributionSha256Sum=39e2d5803bbd5eaf6c8efe07067b0e5a00235e8c71318642b2ed262920b27721