If xcode_backend.sh script fails or substitute variables are missing, fail the...

If xcode_backend.sh script fails or substitute variables are missing, fail the host Xcode build (#37449)

dev/devicelab/bin/tasks/module_test_ios.dart

@@ -276,6 +276,33 @@ Future<void> main() async {
         );
       }
 
+      section('Fail building existing iOS app if flutter script fails');
+      int xcodebuildExitCode = 0;
+      await inDirectory(hostApp, () async {
+        xcodebuildExitCode = await exec(
+          'xcodebuild',
+          <String>[
+            '-workspace',
+            'Host.xcworkspace',
+            '-scheme',
+            'Host',
+            '-configuration',
+            'Debug',
+            'ARCHS=i386', // i386 is not supported in Debug mode.
+            'CODE_SIGNING_ALLOWED=NO',
+            'CODE_SIGNING_REQUIRED=NO',
+            'CODE_SIGN_IDENTITY=-',
+            'EXPANDED_CODE_SIGN_IDENTITY=-',
+            'CONFIGURATION_BUILD_DIR=${tempDir.path}',
+          ],
+          canFail: true
+        );
+      });
+
+      if (xcodebuildExitCode != 65) { // 65 returned on PhaseScriptExecution failure.
+        return TaskResult.failure('Host app build succeeded though flutter script failed');
+      }
+
       return TaskResult.success(null);
     } catch (e) {
       return TaskResult.failure(e.toString());

dev/integration_tests/ios_add2app/ios_add2app.xcodeproj/project.pbxproj

@@ -3,7 +3,7 @@
 	archiveVersion = 1;
 	classes = {
 	};
-	objectVersion = 50;
+	objectVersion = 51;
 	objects = {
 
 /* Begin PBXBuildFile section */
@@ -338,7 +338,7 @@
 			name = "[CP-User] Run Flutter Build Script";
 			runOnlyForDeploymentPostprocessing = 0;
 			shellPath = /bin/sh;
-			shellScript = "source \"${SRCROOT}/flutterapp/.ios/Flutter/flutter_export_environment.sh\"\n\"$FLUTTER_ROOT\"/packages/flutter_tools/bin/xcode_backend.sh build";
+			shellScript = "set -e\nset -u\nsource \"${SRCROOT}/flutterapp/.ios/Flutter/flutter_export_environment.sh\"\n\"$FLUTTER_ROOT\"/packages/flutter_tools/bin/xcode_backend.sh build\n";
 		};
 		DE5CDCD8B3565EAB9F38F455 /* [CP] Check Pods Manifest.lock */ = {
 			isa = PBXShellScriptBuildPhase;

packages/flutter_tools/templates/module/ios/library/Flutter.tmpl/podhelper.rb.tmpl

@@ -89,7 +89,7 @@ def install_flutter_application_pod(flutter_application_path)
 
   flutter_export_environment_path = File.join('${SRCROOT}', relative, 'flutter_export_environment.sh');
   script_phase :name => 'Run Flutter Build Script',
-    :script => "source \"#{flutter_export_environment_path}\"\n\"$FLUTTER_ROOT\"/packages/flutter_tools/bin/xcode_backend.sh build",
+    :script => "set -e\nset -u\nsource \"#{flutter_export_environment_path}\"\n\"$FLUTTER_ROOT\"/packages/flutter_tools/bin/xcode_backend.sh build",
     :input_files => [
       File.join('${SRCROOT}', flutter_application_path, '.metadata'),
       File.join('${SRCROOT}', relative, 'App.framework', 'App'),