Fix hdiutil blank DMG creation on macOS CI runners.

Drop -format UDRW when creating a sized empty image; macOS requires -srcfolder if -format is set.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: lmangani

scripts/build-installer-pkg.sh

@@ -82,12 +82,12 @@ create_dmg_from_app() {
   rm -f "$tmp_rw" "$dmg_path"
 
   echo "Creating ${dmg_mb}MB DMG for ${src_mb}MB app (free: $(disk_free))..."
+  # Blank read-write image: do not pass -format without -srcfolder (macOS rejects it).
   hdiutil create \
     -size "${dmg_mb}m" \
     -volname "$volname" \
     -fs HFS+ \
     -layout SPUD \
-    -format UDRW \
     -ov \
     "$tmp_rw"