Fixes to support add2app on iOS (#22277)

* Fix xcode_backend.sh script to support add2app

* Fix ios deployment target. Too old for new Xcode.

* Fix ios host app

* Register plugins with Flutter view

dev/integration_tests/ios_host_app/Config/Debug.xcconfig

 #include "Flutter.xcconfig"
-#include "Pods/Target Support Files/Pods-Host/Pods-Host.debug.xcconfig"
+#include "../Pods/Target Support Files/Pods-Host/Pods-Host.debug.xcconfig"

dev/integration_tests/ios_host_app/Config/Release.xcconfig

 #include "Flutter.xcconfig"
-#include "Pods/Target Support Files/Pods-Host/Pods-Host.release.xcconfig"
+#include "../Pods/Target Support Files/Pods-Host/Pods-Host.release.xcconfig"
 FLUTTER_BUILD_MODE=release

dev/integration_tests/ios_host_app/Host/AppDelegate.h

@@ -3,3 +3,4 @@
 
 @interface AppDelegate : FlutterAppDelegate
 @end
+

dev/integration_tests/ios_host_app/Host/Base.lproj/LaunchScreen.storyboard

 <?xml version="1.0" encoding="UTF-8" standalone="no"?>
-<document type="com.apple.InterfaceBuilder3.CocoaTouch.Storyboard.XIB" version="3.0" toolsVersion="13122.16" systemVersion="17A277" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" launchScreen="YES" useTraitCollections="YES" useSafeAreas="YES" colorMatched="YES" initialViewController="01J-lp-oVM">
+<document type="com.apple.InterfaceBuilder3.CocoaTouch.Storyboard.XIB" version="3.0" toolsVersion="13122.16" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" launchScreen="YES" useTraitCollections="YES" useSafeAreas="YES" colorMatched="YES" initialViewController="01J-lp-oVM">
     <dependencies>
         <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="13104.12"/>
         <capability name="Safe area layout guides" minToolsVersion="9.0"/>

dev/integration_tests/ios_host_app/Host/Base.lproj/Main.storyboard

 <?xml version="1.0" encoding="UTF-8"?>
-<document type="com.apple.InterfaceBuilder3.CocoaTouch.Storyboard.XIB" version="3.0" toolsVersion="13122.16" systemVersion="17A277" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES" useSafeAreas="YES" colorMatched="YES" initialViewController="BYZ-38-t0r">
+<document type="com.apple.InterfaceBuilder3.CocoaTouch.Storyboard.XIB" version="3.0" toolsVersion="13122.16" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES" useSafeAreas="YES" colorMatched="YES" initialViewController="BYZ-38-t0r">
     <dependencies>
         <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="13104.12"/>
         <capability name="Safe area layout guides" minToolsVersion="9.0"/>

dev/integration_tests/ios_host_app/Host/ViewController.m

@@ -3,6 +3,7 @@
 #import "FlutterPluginRegistrant/GeneratedPluginRegistrant.h"
 
 @implementation ViewController
+
 - (void)viewDidLoad {
     [super viewDidLoad];
     UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
@@ -20,4 +21,5 @@
     [GeneratedPluginRegistrant registerWithRegistry:flutterViewController];
     [self presentViewController:flutterViewController animated:false completion:nil];
 }
+
 @end

dev/integration_tests/ios_host_app/Podfile

@@ -2,5 +2,5 @@ platform :ios, '9.0'
 
 target 'Host' do
   flutter_application_path = '../hello'
-  eval(File.read(File.join(flutter_application_path, '.ios', 'Flutter', 'podhelper.rb')), binding)
+  eval(File.read("#{flutter_application_path}/.ios/Flutter/podhelper.rb"))
 end

packages/flutter_tools/bin/xcode_backend.sh

@@ -81,7 +81,7 @@ BuildApp() {
 
   local derived_dir="${SOURCE_ROOT}/Flutter"
   if [[ -e "${project_path}/.ios" ]]; then
-    derived_dir="${SOURCE_ROOT}/../.ios/Flutter"
+    derived_dir="${project_path}/.ios/Flutter"
   fi
   RunCommand mkdir -p -- "$derived_dir"
   AssertExists "$derived_dir"

packages/flutter_tools/lib/src/plugins.dart

@@ -224,7 +224,7 @@ Depends on all your plugins, and provides a function to register them.
   s.homepage         = 'https://flutter.io'
   s.license          = { :type => 'BSD' }
   s.author           = { 'Flutter Dev Team' => 'flutter-dev@googlegroups.com' }
-  s.ios.deployment_target = '7.0'
+  s.ios.deployment_target = '8.0'
   s.source_files =  "Classes", "Classes/**/*.{h,m}"
   s.source           = { :path => '.' }
   s.public_header_files = './Classes/**/*.h'