Fixed clean building federated programs

core/src/main/java/org/lflang/generator/GeneratorBase.java

@@ -618,7 +618,7 @@ public void reportCommandErrors(String stderr) {
 
   /** Check if a clean was requested from the standalone compiler and perform the clean step. */
   protected void cleanIfNeeded(LFGeneratorContext context) {
-    if (context.getArgs().clean()) {
+    if (context.isCleanRequested()) {
       try {
         context.getFileConfig().doClean();
       } catch (IOException e) {

core/src/main/java/org/lflang/generator/LFGeneratorContext.java

@@ -38,6 +38,11 @@ enum Mode {
   /** Get the error reporter for this context; construct one if it hasn't been constructed yet. */
   MessageReporter getErrorReporter();
 
+  /** Return true if the user requested a clean build in this context. */
+  default boolean isCleanRequested() {
+    return getArgs().clean();
+  }
+
   /**
    * Mark the code generation process performed in this context as finished with the result {@code
    * result}.

core/src/main/java/org/lflang/generator/SubContext.java

@@ -38,6 +38,11 @@ public SubContext(
     this.endPercentProgress = endPercentProgress;
   }
 
+  @Override
+  public boolean isCleanRequested() {
+    return false;
+  } /// never clean in a sub context
+
   @Override
   public CancelIndicator getCancelIndicator() {
     return containingContext.getCancelIndicator();