[core] Add StanzaBuilder.build()

smack-core/src/main/java/org/jivesoftware/smack/packet/IqBuilder.java

@@ -43,6 +43,7 @@ public abstract class IqBuilder<IB extends IqBuilder<IB, I>, I extends IQ>
         return getThis();
     }
 
+    @Override
     public abstract I build();
 
 }

smack-core/src/main/java/org/jivesoftware/smack/packet/IqData.java

@@ -1,6 +1,6 @@
 /**
  *
- * Copyright 2019 Florian Schmaus
+ * Copyright 2019-2020 Florian Schmaus
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -41,4 +41,9 @@ public final class IqData extends AbstractIqBuilder<IqData> {
     public IqData getThis() {
         return this;
     }
+
+    @Override
+    public Stanza build() {
+        throw new UnsupportedOperationException();
+    }
 }

smack-core/src/main/java/org/jivesoftware/smack/packet/MessageOrPresenceBuilder.java

@@ -37,6 +37,7 @@ public abstract class MessageOrPresenceBuilder<MP extends MessageOrPresence<? ex
         super(stanzaId);
     }
 
+    @Override
     public abstract MP build();
 
 }

smack-core/src/main/java/org/jivesoftware/smack/packet/StanzaBuilder.java

@@ -1,6 +1,6 @@
 /**
  *
- * Copyright 2019 Florian Schmaus
+ * Copyright 2019-2020 Florian Schmaus
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -184,6 +184,8 @@ public abstract class StanzaBuilder<B extends StanzaBuilder<B>> implements Stanz
         return getThis();
     }
 
+    public abstract Stanza build();
+
     public abstract B getThis();
 
     @Override