Skip retained published archives when planning builds

build/build.sh

@@ -531,9 +531,17 @@ check_needs_build() {
 
   if [[ "$local_version" == "$pkgbuild_version" ]]; then
     return 1  # Already up to date
-  else
-    return 0  # Needs building
   fi
+
+  # Match check-versions: a retained archive is already published even when
+  # the DB now indexes a newer release (for example, 4.0.4rc1 vs 4.0.3).
+  # Rebuilding it would produce different bytes under an immutable filename.
+  if package_version_is_published "$FINAL_OUTPUT_DIR" "$pkg" "$pkgbuild_version" "$ARCH"; then
+    echo "  + $pkg $pkgbuild_version - archive already published; skipping rebuild"
+    return 1
+  fi
+
+  return 0  # Needs building
 }
 
 # Collect packages that should be built for the selected mirror