gradle: Update to gradle 5.6

build.gradle

@@ -110,6 +110,10 @@ subprojects {
         options.encoding = 'UTF-8'
     }
 
+    tasks.withType(GroovyCompile).configureEach {
+        options.incremental = true
+    }
+
     repositories {
         mavenLocal()
 
@@ -145,7 +149,7 @@ subprojects {
 }
 
 wrapper {
-    gradleVersion = '5.5.1'
+    gradleVersion = '5.6'
 
     doLast {
         def optsEnvVar = "DEFAULT_JVM_OPTS"