Use async execution for xcodebuild commands (#29048)

packages/flutter_tools/lib/src/ios/mac.dart

@@ -311,7 +311,7 @@ Future<XcodeBuildResult> buildXcodeProject({
     modern: false,
   );
 
-  final XcodeProjectInfo projectInfo = xcodeProjectInterpreter.getInfo(app.project.hostAppRoot.path);
+  final XcodeProjectInfo projectInfo = await xcodeProjectInterpreter.getInfo(app.project.hostAppRoot.path);
   if (!projectInfo.targets.contains('Runner')) {
     printError('The Xcode project does not define target "Runner" which is needed by Flutter tooling.');
     printError('Open Xcode to fix the problem:');

packages/flutter_tools/lib/src/ios/xcodeproj.dart

@@ -161,11 +161,11 @@ class XcodeProjectInterpreter {
     return parseXcodeBuildSettings(out);
   }
 
-  XcodeProjectInfo getInfo(String projectPath) {
-    final String out = runCheckedSync(<String>[
+  Future<XcodeProjectInfo> getInfo(String projectPath) async {
+    final RunResult result = await runCheckedAsync(<String>[
       _executable, '-list',
     ], workingDirectory: projectPath);
-    return XcodeProjectInfo.fromXcodeBuildOutput(out);
+    return XcodeProjectInfo.fromXcodeBuildOutput(result.toString());
   }
 }
 

packages/flutter_tools/test/src/context.dart

@@ -294,7 +294,7 @@ class MockXcodeProjectInterpreter implements XcodeProjectInterpreter {
   }
 
   @override
-  XcodeProjectInfo getInfo(String projectPath) {
+  Future<XcodeProjectInfo> getInfo(String projectPath) async {
     return XcodeProjectInfo(
       <String>['Runner'],
       <String>['Debug', 'Release'],