Ensure iOS platform before TestFlight archive (#8656)

ci/github_actions/archive_ios.sh

@@ -46,6 +46,45 @@ fi
 SCHEME="Unity-iPhone"
 echo "Using scheme: $SCHEME"
 
+# Xcode can be upgraded on a self-hosted runner before its matching iOS platform
+# component is installed. In that state, xcrun may exist but the generic iOS
+# destination is ineligible, and archive fails with exit code 70. Probe the exact
+# destination used below and repair the Xcode installation before starting the
+# expensive archive.
+if ! xcodebuild \
+    -project "$XCODEPROJ" \
+    -scheme "$SCHEME" \
+    -showBuildSettings \
+    -destination "generic/platform=iOS" >/dev/null; then
+    echo "The generic iOS destination is unavailable; installing Xcode's iOS platform..."
+
+    if ! xcodebuild -checkFirstLaunchStatus; then
+        echo "Completing pending Xcode first-launch setup..."
+        xcodebuild -runFirstLaunch
+    fi
+
+    xcodebuild -downloadPlatform iOS
+fi
+
+echo "Installed Xcode SDKs:"
+xcodebuild -showsdks
+IOS_SDK_PATH=$(xcrun --sdk iphoneos --show-sdk-path)
+if [ ! -d "$IOS_SDK_PATH" ]; then
+    echo "Error: Xcode reported an invalid iOS SDK path: $IOS_SDK_PATH"
+    exit 1
+fi
+echo "Using iOS SDK: $IOS_SDK_PATH"
+
+if ! xcodebuild \
+    -project "$XCODEPROJ" \
+    -scheme "$SCHEME" \
+    -showBuildSettings \
+    -destination "generic/platform=iOS" >/dev/null; then
+    echo "Error: The generic iOS destination is still unavailable after platform setup."
+    xcodebuild -project "$XCODEPROJ" -scheme "$SCHEME" -showdestinations || true
+    exit 1
+fi
+
 # Archive without signing - we'll sign during export
 # This avoids issues with provisioning profiles on framework targets
 xcodebuild archive \