Added a CompilerProgressListenerList to the EditorStatus class so you can add a listener for compiler progress from an external tool. To enable this the build method in the compiler class had to be changed

app/src/processing/app/Editor.java

@@ -29,6 +29,7 @@ import cc.arduino.packages.uploaders.SerialUploader;
 import cc.arduino.view.GoToLineNumber;
 import cc.arduino.view.StubMenuListener;
 import cc.arduino.view.findreplace.FindReplace;
+import cc.arduino.CompilerProgressListener;
 import com.jcraft.jsch.JSchException;
 import jssc.SerialPortException;
 import processing.app.debug.RunnerException;
@@ -65,6 +66,7 @@ import java.util.List;
 import java.util.function.Predicate;
 import java.util.zip.ZipEntry;
 import java.util.zip.ZipFile;
+import java.util.ArrayList;
 
 import static processing.app.I18n.tr;
 import static processing.app.Theme.scale;
@@ -2691,5 +2693,8 @@ public class Editor extends JFrame implements RunnerListener {
     lineStatus.repaint();
   }
 
+  public void addCompilerProgressListener(CompilerProgressListener listener){
+    this.status.addCompilerProgressListener(listener);
+  }
 
 }

app/src/processing/app/EditorStatus.java

@@ -24,6 +24,7 @@
 package processing.app;
 
 import processing.app.helpers.OSUtils;
+import cc.arduino.CompilerProgressListener;
 
 import javax.swing.*;
 import java.awt.*;
@@ -31,6 +32,7 @@ import java.awt.datatransfer.Clipboard;
 import java.awt.datatransfer.StringSelection;
 import java.awt.event.KeyAdapter;
 import java.awt.event.KeyEvent;
+import java.util.ArrayList;
 
 import static processing.app.I18n.tr;
 import static processing.app.Theme.scale;
@@ -89,11 +91,15 @@ public class EditorStatus extends JPanel {
   private JProgressBar progressBar;
   private JButton copyErrorButton;
   
+  private ArrayList<CompilerProgressListener> compilerProgressListeners;
+
   public EditorStatus(Editor editor) {
     this.editor = editor;
     this.message = NO_MESSAGE;
     this.mode = NOTICE;
     this.font = Theme.getFont("status.font");
+    this.compilerProgressListeners = new ArrayList<CompilerProgressListener>();
+    this.compilerProgressListeners.add(this::progressUpdate);
     initialize();
   }
 
@@ -410,4 +416,12 @@ public class EditorStatus extends JPanel {
     return mode == ERR;
   }
   
+  public void addCompilerProgressListener(CompilerProgressListener listener){
+    compilerProgressListeners.add(listener);
+  }
+  
+  public ArrayList<CompilerProgressListener> getCompilerProgressListeners(){
+    return compilerProgressListeners;
+  }
+
 }

app/src/processing/app/SketchController.java

@@ -627,11 +627,12 @@ public class SketchController {
    */
   public String build(boolean verbose, boolean save) throws RunnerException, PreferencesMapException, IOException {
     // run the preprocessor
-    editor.status.progressUpdate(20);
+    for (CompilerProgressListener progressListener : editor.status.getCompilerProgressListeners()){
+      progressListener.progress(20);
+    }
 
     ensureExistence();
        
-    CompilerProgressListener progressListener = editor.status::progressUpdate;
 
     boolean deleteTemp = false;
     File pathToSketch = sketch.getPrimaryFile().getFile();
@@ -643,7 +644,7 @@ public class SketchController {
     }
 
     try {
-      return new Compiler(pathToSketch, sketch).build(progressListener, save);
+      return new Compiler(pathToSketch, sketch).build(editor.status.getCompilerProgressListeners(), save);
     } finally {
       // Make sure we clean up any temporary sketch copy
       if (deleteTemp)

arduino-core/src/cc/arduino/Compiler.java

@@ -152,6 +152,12 @@ public class Compiler implements MessageConsumer {
   }
 
   public String build(CompilerProgressListener progListener, boolean exportHex) throws RunnerException, PreferencesMapException, IOException {
+    ArrayList<CompilerProgressListener> listeners = new ArrayList<CompilerProgressListener>();
+    listeners.add(progListener);
+    return this.build(listeners, exportHex);
+  }
+  
+  public String build(ArrayList<CompilerProgressListener> progListeners, boolean exportHex) throws RunnerException, PreferencesMapException, IOException {
     this.buildPath = sketch.getBuildPath().getAbsolutePath();
 
     TargetBoard board = BaseNoGui.getTargetBoard();
@@ -165,7 +171,7 @@ public class Compiler implements MessageConsumer {
 
     PreferencesMap prefs = loadPreferences(board, platform, aPackage, vidpid);
 
-    MessageConsumerOutputStream out = new MessageConsumerOutputStream(new ProgressAwareMessageConsumer(new I18NAwareMessageConsumer(System.out, System.err), progListener), "\n");
+    MessageConsumerOutputStream out = new MessageConsumerOutputStream(new ProgressAwareMessageConsumer(new I18NAwareMessageConsumer(System.out, System.err), progListeners), "\n");
     MessageConsumerOutputStream err = new MessageConsumerOutputStream(new I18NAwareMessageConsumer(System.err, Compiler.this), "\n");
 
     callArduinoBuilder(board, platform, aPackage, vidpid, BuilderAction.COMPILE, out, err);

arduino-core/src/cc/arduino/ProgressAwareMessageConsumer.java

@@ -33,16 +33,17 @@ import cc.arduino.i18n.ExternalProcessOutputParser;
 import processing.app.debug.MessageConsumer;
 
 import java.util.Map;
+import java.util.ArrayList;
 
 public class ProgressAwareMessageConsumer implements MessageConsumer {
 
   private final MessageConsumer parent;
-  private final CompilerProgressListener progressListener;
+  private ArrayList<CompilerProgressListener> progressListeners;
   private final ExternalProcessOutputParser parser;
 
-  public ProgressAwareMessageConsumer(MessageConsumer parent, CompilerProgressListener progressListener) {
+  public ProgressAwareMessageConsumer(MessageConsumer parent, ArrayList<CompilerProgressListener> progressListeners) {
     this.parent = parent;
-    this.progressListener = progressListener;
+    this.progressListeners = progressListeners;
     this.parser = new ExternalProcessOutputParser();
   }
 
@@ -51,7 +52,9 @@ public class ProgressAwareMessageConsumer implements MessageConsumer {
     if (s.startsWith("===info ||| Progress") || s.startsWith("===Progress")) {
       Map<String, Object> parsedMessage = parser.parse(s);
       Object[] args = (Object[]) parsedMessage.get("args");
-      progressListener.progress(Double.valueOf(args[0].toString()).intValue());
+      for (CompilerProgressListener progressListener : progressListeners){
+        progressListener.progress(Double.valueOf(args[0].toString()).intValue());
+      }
       return;
     }