Update Gradle to 6.8.3 (#2561)

gradle/java.gradle

@@ -40,9 +40,6 @@ if (project.hasProperty("minJavaVersionForTests")) {
 }
 
 java {
-  sourceCompatibility = JavaVersion.toVersion(project.ext.release)
-  targetCompatibility = JavaVersion.toVersion(project.ext.release)
-
   toolchain {
     languageVersion = JavaLanguageVersion.of(Math.max(project.ext.release.majorVersion.toInteger(), DEFAULT_JAVA_VERSION))
   }
@@ -54,13 +51,16 @@ java {
 }
 
 tasks.withType(JavaCompile) {
-  options.release = project.ext.release.majorVersion.toInteger()
+  options.release.set(project.ext.release.majorVersion.toInteger())
 }
+//Groovy and Scala compilers don't actually understand --release option
 tasks.withType(GroovyCompile) {
-  options.release = project.ext.release.majorVersion.toInteger()
+  sourceCompatibility = JavaVersion.toVersion(project.ext.release)
+  targetCompatibility = JavaVersion.toVersion(project.ext.release)
 }
 tasks.withType(ScalaCompile) {
-  options.release = project.ext.release.majorVersion.toInteger()
+  sourceCompatibility = JavaVersion.toVersion(project.ext.release)
+  targetCompatibility = JavaVersion.toVersion(project.ext.release)
 }
 
 apply plugin: "eclipse"

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.7.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.8.3-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionSha256Sum=3239b5ed86c3838a37d983ac100573f64c1f3fd8e1eb6c89fa5f9529b5ec091d
+distributionSha256Sum=7faa7198769f872826c8ef4f1450f839ec27f0b4d5d1e51bade63667cbccd205

instrumentation/apache-camel-2.20/javaagent/apache-camel-2.20-javaagent.gradle

@@ -1,7 +1,3 @@
-ext {
-  minJavaVersionForTests = JavaVersion.VERSION_1_8
-}
-
 apply from: "$rootDir/gradle/instrumentation.gradle"
 
 muzzle {

instrumentation/rmi/javaagent/rmi-javaagent.gradle

@@ -25,6 +25,8 @@ test.dependsOn "rmic"
 // We also can't seem to use the toolchain without the "--release" option. So disable everything.
 
 java {
+  sourceCompatibility = JavaVersion.toVersion(project.ext.release)
+  targetCompatibility = JavaVersion.toVersion(project.ext.release)
   toolchain {
     languageVersion = null
   }