Make host app test actually test host app (#24131) * Make host app test actually test host app * mark updated test as flaky

diff --git a/dev/devicelab/bin/tasks/module_test_ios.dart b/dev/devicelab/bin/tasks/module_test_ios.dart
index af3cb69..284455c 100644
--- a/dev/devicelab/bin/tasks/module_test_ios.dart
+++ b/dev/devicelab/bin/tasks/module_test_ios.dart

@@ -14,7 +14,6 @@
 /// adding Flutter to an existing iOS app.
 Future<void> main() async {
   await task(() async {
-
     section('Create Flutter module project');
 
     final Directory tempDir = Directory.systemTemp.createTempSync('flutter_module_test.');
@@ -23,7 +22,12 @@
       await inDirectory(tempDir, () async {
         await flutter(
           'create',
-          options: <String>['--org', 'io.flutter.devicelab', '--template=module', 'hello'],
+          options: <String>[
+            '--org',
+            'io.flutter.devicelab',
+            '--template=module',
+            'hello'
+          ],
         );
       });
       await prepareProvisioningCertificates(projectDir.path);
@@ -127,11 +131,51 @@
       if (!editableHostAppBuilt) {
         return TaskResult.failure('Failed to build editable host .app');
       }
+
+      section('Add to existing iOS app');
+
+      final Directory hostApp = Directory(path.join(tempDir.path, 'hello_host_app'));
+      mkdir(hostApp);
+      recursiveCopy(
+        Directory(path.join(flutterDirectory.path, 'dev', 'integration_tests', 'ios_host_app')),
+        hostApp,
+      );
+
+      await inDirectory(hostApp, () async {
+        await exec('pod', <String>['install']);
+        await exec(
+          'xcodebuild',
+          <String>[
+            '-workspace',
+            'Host.xcworkspace',
+            '-scheme',
+            'Host',
+            '-configuration',
+            'Debug',
+            'CODE_SIGNING_ALLOWED=NO',
+            'CODE_SIGNING_REQUIRED=NO',
+            'CODE_SIGNING_IDENTITY=""',
+            'EXPANDED_CODE_SIGN_IDENTITY=""',
+            'CONFIGURATION_BUILD_DIR=${tempDir.path}',
+          ],
+        );
+      });
+
+      final bool existingAppBuilt = exists(File(path.join(
+        tempDir.path,
+        'Host.app',
+        'Host',
+      )));
+
+      if (!existingAppBuilt) {
+        return TaskResult.failure('Failed to build existing app .app');
+      }
+
       return TaskResult.success(null);
     } catch (e) {
       return TaskResult.failure(e.toString());
     } finally {
-      //rmTree(tempDir);
+      rmTree(tempDir);
     }
   });
 }

diff --git a/dev/devicelab/manifest.yaml b/dev/devicelab/manifest.yaml
index 2a19670..1756792 100644
--- a/dev/devicelab/manifest.yaml
+++ b/dev/devicelab/manifest.yaml

@@ -326,6 +326,7 @@
       Checks that the module project template works and supports add2app on iOS.
     stage: devicelab
     required_agent_capabilities: ["mac/ios"]
+    flaky: true
 
   external_ui_integration_test_ios:
     description: >

diff --git a/dev/integration_tests/ios_host_app/Host.xcodeproj/project.pbxproj b/dev/integration_tests/ios_host_app/Host.xcodeproj/project.pbxproj
index a807ebc..1ed979e 100644
--- a/dev/integration_tests/ios_host_app/Host.xcodeproj/project.pbxproj
+++ b/dev/integration_tests/ios_host_app/Host.xcodeproj/project.pbxproj

@@ -234,7 +234,7 @@
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 			shellPath = /bin/sh;
-			shellScript = "\"$FLUTTER_ROOT/packages/flutter_tools/bin/xcode_backend.sh\" build\n";
+			shellScript = "\"$FLUTTER_ROOT/packages/flutter_tools/bin/xcode_backend.sh\" build\n\"$FLUTTER_ROOT/packages/flutter_tools/bin/xcode_backend.sh\" embed\n";
 		};
 		EDACAC7378E52BD5BBDB34D5 /* [CP] Check Pods Manifest.lock */ = {
 			isa = PBXShellScriptBuildPhase;

diff --git a/dev/integration_tests/ios_host_app/README.md b/dev/integration_tests/ios_host_app/README.md
new file mode 100644
index 0000000..9b71d99
--- /dev/null
+++ b/dev/integration_tests/ios_host_app/README.md

@@ -0,0 +1,8 @@
+# iOS host app
+
+iOS host app for a Flutter module created using
+```
+$ flutter create -t module hello
+```
+and placed in a sibling folder to (a clone of) the host app.
+Used by the `module_test_ios.dart` device lab test.

diff --git a/packages/flutter_tools/bin/xcode_backend.sh b/packages/flutter_tools/bin/xcode_backend.sh
index acdcf56..8973f9c 100755
--- a/packages/flutter_tools/bin/xcode_backend.sh
+++ b/packages/flutter_tools/bin/xcode_backend.sh

@@ -367,9 +367,10 @@
   
   # Sign the binaries we moved.
   local identity="${EXPANDED_CODE_SIGN_IDENTITY_NAME:-$CODE_SIGN_IDENTITY}"
-
-  RunCommand codesign --force --verbose --sign "${identity}" -- "${xcode_frameworks_dir}/App.framework/App"
-  RunCommand codesign --force --verbose --sign "${identity}" -- "${xcode_frameworks_dir}/Flutter.framework/Flutter"
+  if (${identity} != ""); then
+    RunCommand codesign --force --verbose --sign "${identity}" -- "${xcode_frameworks_dir}/App.framework/App"
+    RunCommand codesign --force --verbose --sign "${identity}" -- "${xcode_frameworks_dir}/Flutter.framework/Flutter"
+  fi
 }
 
 # Main entry point.

diff --git a/packages/flutter_tools/templates/module/ios/library/Flutter.tmpl/podhelper.rb b/packages/flutter_tools/templates/module/ios/library/Flutter.tmpl/podhelper.rb
index f98153a..bdd3313c 100644
--- a/packages/flutter_tools/templates/module/ios/library/Flutter.tmpl/podhelper.rb
+++ b/packages/flutter_tools/templates/module/ios/library/Flutter.tmpl/podhelper.rb

@@ -68,7 +68,7 @@
             config.build_settings['ENABLE_BITCODE'] = 'NO'
             xcconfig_path = config.base_configuration_reference.real_path
             File.open(xcconfig_path, 'a+') do |file|
-                file.puts "#include \"#{File.join(framework_dir, 'Generated.xcconfig')}\""
+                file.puts "#include \"#{File.realpath(File.join(framework_dir, 'Generated.xcconfig'))}\""
             end
         end
     end