Force garbage finalization and another gc run in gradle tests.

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/CleanUpBuildListener.kt

@@ -85,6 +85,8 @@ class CleanUpBuildListener(pluginClassLoader: ClassLoader, private val project:
 
         log.lifecycle(FORCE_SYSTEM_GC_MESSAGE)
         System.gc()
+        System.runFinalization()
+        System.gc()
         val rt = Runtime.getRuntime()
         return (rt.totalMemory() - rt.freeMemory()) / 1024
     }