Umbrella issue tracking developing Flutter apps working with Xcode 12.

• Fix all "Double-quoted include in framework header, expected angle-bracketed instead" warnings #60025 Fix all "Double-quoted include in framework header, expected angle-bracketed instead" warnings
• Migrate existing plugins with minimum supported iOS version from 8.0 to 9.0 #62880 Migrate existing apps/plugins with minimum supported iOS version from 8.0 to 9.0

Available in 1.22

• Increase app template minimum supported iOS version from 8.0 to 9.0 #60035 Increase app template minimum supported iOS version from 8.0 to 9.0
• build_ios_framework_module_test fails with Xcode 12 #60043 build_ios_framework_module_test fails with Xcode 12
• flutter run fails Xcode 12: fruitstrap_.py, in connect_command process = lldb.target.ConnectRemote(listener, connect_url, None, error) AttributeError: 'NoneType' object has no attribute 'ConnectRemote' #60072 flutter run fails Xcode 12: fruitstrap_.py, in connect_command process
• Bump Cirrus image Xcode version #63252 Bump Cirrus image Xcode version
• Engine doesn't build in Xcode 12 #63613 Engine doesn't build in Xcode 12

Available in 1.23.0-13.0.pre

• Increase plugin template minimum supported iOS version from 8.0 to 9.0 #63253 Increase plugin template minimum supported iOS version from 8.0 to 9.0

Related umbrella issues

iOS 14 support tracked separately at #61047.
ARM macOS host tracked separately at #60118.