Include Swift extensions in zip and Carthage (#9471)

scripts/setup_quickstart_framework.sh

@@ -28,6 +28,11 @@ if [[ ! -z "$LEGACY" ]]; then
   cd "Legacy${SAMPLE}Quickstart"
 fi
 
+# Make sure the Xcode project has at least one Swift file.
+# See https://forums.swift.org/t/using-binary-swift-sdks-from-non-swift-apps/55989
+touch foo.swift
+"${REPO}"/scripts/update_xcode_target.rb "${SAMPLE}Example.xcodeproj" "${SAMPLE}Example" foo.swift
+
 mkdir -p Firebase/
 # Create non Firebase Frameworks and move to Firebase/ dir.
 if [[ ! -z "$NON_FIREBASE_SDKS" ]]; then