Issue #88: Make Traute work with gradle apt plugin

Avoid throwing/catching exceptions for a project with
many files generated by annotation processors

core/javac/src/main/java/tech/harmonysoft/oss/traute/javac/TrauteJavacPlugin.java

@@ -40,6 +40,7 @@
 import java.lang.reflect.Field;
 import java.util.*;
 import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicReference;
 
 import static java.lang.reflect.Modifier.*;
@@ -125,6 +126,7 @@ public void init(JavacTask task, String... args) {
             )));
         }
         Context context = ((BasicJavacTask) task).getContext();
+        AtomicBoolean contextClosed = new AtomicBoolean();
         TrautePluginSettings settings = getPluginSettings(context);
         pluginSettingsRef.set(settings);
         task.addTaskListener(new TaskListener() {
@@ -218,10 +220,14 @@ public void finished(TaskEvent event) {
              * @return      {@code true} if current context is closed; {@code false} otherwise
              */
             private boolean isContextClosed() {
+                if (contextClosed.get()) {
+                    return true;
+                }
                 try {
                     Log.instance(context);
                     return false;
                 } catch (Exception e) {
+                    contextClosed.set(true);
                     return true;
                 }
             }