Blacklist Gradle 4.2 and above

An upstream Gradle change has broken us starting on version 4.2. This
commit blacklists these versions until we can either find a workaround,
or the upstream issue is addressed.

Relates #27087

Author: jasontedor

buildSrc/src/main/groovy/org/elasticsearch/gradle/BuildPlugin.groovy

@@ -123,12 +123,19 @@ class BuildPlugin implements Plugin<Project> {
             }
             println "  Random Testing Seed   : ${project.testSeed}"
 
-            // enforce gradle version
-            GradleVersion minGradle = GradleVersion.version('3.3')
-            if (GradleVersion.current() < minGradle) {
+            // enforce Gradle version
+            final GradleVersion currentGradleVersion = GradleVersion.current();
+
+            final GradleVersion minGradle = GradleVersion.version('3.3')
+            if (currentGradleVersion < minGradle) {
                 throw new GradleException("${minGradle} or above is required to build elasticsearch")
             }
 
+            final GradleVersion maxGradle = GradleVersion.version('4.2')
+            if (currentGradleVersion >= maxGradle) {
+                throw new GradleException("${maxGradle} or above is not compatible with the elasticsearch build")
+            }
+
             // enforce Java version
             if (javaVersionEnum < minimumJava) {
                 throw new GradleException("Java ${minimumJava} or above is required to build Elasticsearch")