HHH-14111 Ensure Groovy compilation tasks target the same JDK version as the rest of the project

buildSrc/build.gradle

@@ -20,3 +20,9 @@ dependencies {
 	compile 'org.hibernate.build.gradle:gradle-animalSniffer-plugin:1.0.1.Final'
 	compile 'org.hibernate.build.gradle:hibernate-matrix-testing:3.0.0.Final'
 }
+
+tasks.withType( GroovyCompile ) {
+	options.encoding = 'UTF-8'
+	sourceCompatibility = 8
+	targetCompatibility = 8
+}

tooling/hibernate-gradle-plugin/hibernate-gradle-plugin.gradle

@@ -21,3 +21,9 @@ dependencies {
 	compile gradleApi()
 	compile localGroovy()
 }
+
+tasks.withType( GroovyCompile ) {
+	options.encoding = 'UTF-8'
+	sourceCompatibility = project.baselineJavaVersion
+	targetCompatibility = project.baselineJavaVersion
+}