Use options.release only on JDK 10+

Author: Lipen

build.gradle.kts

@@ -72,7 +72,13 @@ allprojects {
 
     tasks {
         withType<JavaCompile> {
-            options.release = 8
+            // See: https://docs.gradle.org/current/userguide/building_java_projects.html#sec:compiling_with_release
+            if (JavaVersion.current().isJava10Compatible) {
+                options.release = 8
+            } else {
+                sourceCompatibility = JavaVersion.VERSION_1_8.toString()
+                targetCompatibility = JavaVersion.VERSION_1_8.toString()
+            }
             options.encoding = "UTF-8"
             options.compilerArgs.add("-Xlint:all")
         }