fix: remove redundant IncrementalProjectBuilder.needRebuild() from BuildContext

BuildContext.needRebuild() served two purposes:
1. Set the internal rebuildRequired flag (consumed by
   RebuildingXtextBuilder.doBuild()'s internal rebuild loop)
2. Call builder.needRebuild() which tells Eclipse to re-invoke
   the entire build() method for this project in the next round

Purpose (2) is redundant because purpose (1) already drives
re-processing of generated sources via the internal loop (up to
2 extra iterations in doBuild()). The Eclipse-level needRebuild()
causes unnecessary re-invocations of the builder that cascade
through the workspace dependency graph: each builder participant
that writes a generated file triggers needRebuild(), Eclipse
re-schedules the project, which produces more workspace changes,
triggering builds in dependent projects, and so on.

This resulted in unrelated projects (e.g. intfdef.core) being
fully rebuilt when editing files in completely unrelated projects
(e.g. assistant.chat.ui).

Remove the builder.needRebuild() call while keeping the internal
rebuildRequired flag that drives the RebuildingXtextBuilder's own
rebuild loop.

Author: joaodinissf

com.avaloq.tools.ddk.xtext.builder/src/com/avaloq/tools/ddk/xtext/builder/BuildContext.java

@@ -117,9 +117,12 @@ public ResourceSet getResourceSet() {
   @Override
   public void needRebuild() {
     rebuildRequired = true;
-    if (builder != null) {
-      builder.needRebuild();
-    }
+    // Don't call builder.needRebuild() here. The RebuildingXtextBuilder's internal
+    // rebuild loop (rebuilds <= 2 in doBuild()) already handles re-processing of
+    // generated sources. Calling builder.needRebuild() additionally tells Eclipse to
+    // re-invoke the entire build() method for this project in the next auto-build round,
+    // which causes redundant builder re-invocations that cascade through the workspace
+    // dependency graph.
   }
 
   /**