Remove Runner target check, prefer schemes (#56620)

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

diff --git a/packages/flutter_tools/lib/src/ios/code_signing.dart b/packages/flutter_tools/lib/src/ios/code_signing.dart
index cce0ae4..ec99325 100644
--- a/packages/flutter_tools/lib/src/ios/code_signing.dart
+++ b/packages/flutter_tools/lib/src/ios/code_signing.dart
@@ -13,6 +13,7 @@
 import '../base/io.dart';
 import '../base/logger.dart';
 import '../base/process.dart';
+import '../build_info.dart';
 import '../convert.dart' show utf8;
 import '../globals.dart' as globals;
 
@@ -101,8 +102,9 @@
   @required BuildableIOSApp iosApp,
   @required ProcessManager processManager,
   @required Logger logger,
+  @required BuildInfo buildInfo,
 }) async {
-  final Map<String, String> buildSettings = await iosApp.project.buildSettings;
+  final Map<String, String> buildSettings = await iosApp.project.buildSettingsForBuildInfo(buildInfo);
   if (buildSettings == null) {
     return null;
   }

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

diff --git a/packages/flutter_tools/lib/src/ios/mac.dart b/packages/flutter_tools/lib/src/ios/mac.dart
index d3d6e92..f2f088d 100644
--- a/packages/flutter_tools/lib/src/ios/mac.dart
+++ b/packages/flutter_tools/lib/src/ios/mac.dart
@@ -111,12 +111,6 @@
   await removeFinderExtendedAttributes(app.project.hostAppRoot, processUtils, globals.logger);
 
   final XcodeProjectInfo projectInfo = await globals.xcodeProjectInterpreter.getInfo(app.project.hostAppRoot.path);
-  if (!projectInfo.targets.contains('Runner')) {
-    globals.printError('The Xcode project does not define target "Runner" which is needed by Flutter tooling.');
-    globals.printError('Open Xcode to fix the problem:');
-    globals.printError('  open ios/Runner.xcworkspace');
-    return XcodeBuildResult(success: false);
-  }
   final String scheme = projectInfo.schemeFor(buildInfo);
   if (scheme == null) {
     globals.printError('');
@@ -180,7 +174,8 @@
     autoSigningConfigs = await getCodeSigningIdentityDevelopmentTeam(
       iosApp: app,
       processManager: globals.processManager,
-      logger: globals.logger
+      logger: globals.logger,
+      buildInfo: buildInfo,
     );
   }
 
@@ -229,7 +224,10 @@
   }
 
   // Check if the project contains a watchOS companion app.
-  final bool hasWatchCompanion = await app.project.containsWatchCompanion(projectInfo.targets);
+  final bool hasWatchCompanion = await app.project.containsWatchCompanion(
+    projectInfo.targets,
+    buildInfo,
+  );
   if (hasWatchCompanion) {
     // The -sdk argument has to be omitted if a watchOS companion app exists.
     // Otherwise the build will fail as WatchKit dependencies cannot be build using the iOS SDK.

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

diff --git a/packages/flutter_tools/lib/src/ios/xcodeproj.dart b/packages/flutter_tools/lib/src/ios/xcodeproj.dart
index 1786508..b2fab77 100644
--- a/packages/flutter_tools/lib/src/ios/xcodeproj.dart
+++ b/packages/flutter_tools/lib/src/ios/xcodeproj.dart
@@ -309,9 +309,12 @@
 
   /// Asynchronously retrieve xcode build settings. This one is preferred for
   /// new call-sites.
+  ///
+  /// If [scheme] is null, xcodebuild will return build settings for the first discovered
+  /// target (by default this is Runner).
   Future<Map<String, String>> getBuildSettings(
-    String projectPath,
-    String target, {
+    String projectPath, {
+    String scheme,
     Duration timeout = const Duration(minutes: 1),
   }) async {
     final Status status = Status.withSpinner(
@@ -324,8 +327,8 @@
       _executable,
       '-project',
       _fileSystem.path.absolute(projectPath),
-      '-target',
-      target,
+      if (scheme != null)
+        ...<String>['-scheme', scheme],
       '-showBuildSettings',
       ...environmentVariablesAsXcodeBuildSettings(_platform)
     ];
@@ -465,7 +468,6 @@
   final List<String> buildConfigurations;
   final List<String> schemes;
 
-  bool get definesCustomTargets => !(targets.contains('Runner') && targets.length == 1);
   bool get definesCustomSchemes => !(schemes.contains('Runner') && schemes.length == 1);
   bool get definesCustomBuildConfigurations {
     return !(buildConfigurations.contains('Debug') &&
@@ -475,7 +477,7 @@
 
   /// The expected scheme for [buildInfo].
   static String expectedSchemeFor(BuildInfo buildInfo) {
-    return toTitleCase(buildInfo.flavor ?? 'runner');
+    return toTitleCase(buildInfo?.flavor ?? 'runner');
   }
 
   /// The expected build configuration for [buildInfo] and [scheme].