[Migration] Xcode 11.4 Support

Issue: Fix "white screen" error when building applications in the IOS simulator

Ticket:

https://github.com/inspireui/support/issues/2503

Solution:

Step 1: call flutter clean

Step 2: Go to the ios folder in the project, open the file Runner.xcworkspace with xcode.

Step 3: Select Runner -> Build Phase -> Thin Binary

Step 4: Modify Thin Binary to:

/bin/sh "$FLUTTER_ROOT/packages/flutter_tools/bin/xcode_backend.sh" embed
/bin/sh "$FLUTTER_ROOT/packages/flutter_tools/bin/xcode_backend.sh" thin

Step 5: Run Build in Xcode