[flutter_tools] correctly forward error only stdout in non-verbose modes (#63815)

dev/integration_tests/flutter_gallery/macos/Runner.xcodeproj/project.pbxproj

@@ -301,7 +301,7 @@
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 			shellPath = /bin/sh;
-			shellScript = "\"$FLUTTER_ROOT\"/packages/flutter_tools/bin/macos_assemble.sh\ntouch Flutter/ephemeral/tripwire\n";
+			shellScript = "\"$FLUTTER_ROOT\"/packages/flutter_tools/bin/macos_assemble.sh && touch Flutter/ephemeral/tripwire";
 		};
 		36C290D58D35783923B6B124 /* [CP] Check Pods Manifest.lock */ = {
 			isa = PBXShellScriptBuildPhase;

packages/flutter_tools/lib/src/macos/build_macos.dart

@@ -14,6 +14,10 @@ import '../ios/xcodeproj.dart';
 import '../project.dart';
 import 'cocoapod_utils.dart';
 
+/// When run in -quiet mode, Xcode only prints from the underlying tasks to stdout.
+/// Passing this regexp to trace moves the stdout output to stderr.
+final RegExp _anyOutput = RegExp('.*');
+
 /// Builds the macOS project through xcodebuild.
 // TODO(jonahwilliams): refactor to share code with the existing iOS code.
 Future<void> buildMacOS({
@@ -87,10 +91,15 @@ Future<void> buildMacOS({
       'OBJROOT=${globals.fs.path.join(flutterBuildDir.absolute.path, 'Build', 'Intermediates.noindex')}',
       'SYMROOT=${globals.fs.path.join(flutterBuildDir.absolute.path, 'Build', 'Products')}',
       if (verboseLogging)
-        'VERBOSE_SCRIPT_LOGGING=YES',
+        'VERBOSE_SCRIPT_LOGGING=YES'
+      else
+        '-quiet',
       'COMPILER_INDEX_STORE_ENABLE=NO',
       ...environmentVariablesAsXcodeBuildSettings(globals.platform)
-    ], trace: true);
+    ],
+    trace: true,
+    stdoutErrorMatcher: verboseLogging ? null : _anyOutput,
+  );
   } finally {
     status.cancel();
   }

packages/flutter_tools/templates/app/macos.tmpl/Runner.xcodeproj/project.pbxproj.tmpl

@@ -280,7 +280,7 @@
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 			shellPath = /bin/sh;
-			shellScript = "\"$FLUTTER_ROOT\"/packages/flutter_tools/bin/macos_assemble.sh\ntouch Flutter/ephemeral/tripwire\n";
+			shellScript = "\"$FLUTTER_ROOT\"/packages/flutter_tools/bin/macos_assemble.sh && touch Flutter/ephemeral/tripwire";
 		};
 /* End PBXShellScriptBuildPhase section */
 

packages/flutter_tools/test/commands.shard/hermetic/build_macos_test.dart

@@ -86,7 +86,9 @@ void main() {
         'OBJROOT=${fileSystem.path.join(flutterBuildDir.absolute.path, 'Build', 'Intermediates.noindex')}',
         'SYMROOT=${fileSystem.path.join(flutterBuildDir.absolute.path, 'Build', 'Products')}',
         if (verbose)
-          'VERBOSE_SCRIPT_LOGGING=YES',
+          'VERBOSE_SCRIPT_LOGGING=YES'
+        else
+          '-quiet',
         'COMPILER_INDEX_STORE_ENABLE=NO',
       ],
       stdout: 'STDOUT STUFF',
@@ -129,7 +131,7 @@ void main() {
     FeatureFlags: () => TestFeatureFlags(isMacOSEnabled: true),
   });
 
-  testUsingContext('macOS build does not spew stdout to status logger', () async {
+  testUsingContext('macOS build forwards error stdout to status logger error', () async {
     final BuildCommand command = BuildCommand();
     createMinimalMockProjectFiles();
 
@@ -137,7 +139,8 @@ void main() {
       const <String>['build', 'macos', '--debug']
     );
     expect(testLogger.statusText, isNot(contains('STDOUT STUFF')));
-    expect(testLogger.traceText, contains('STDOUT STUFF'));
+    expect(testLogger.traceText, isNot(contains('STDOUT STUFF')));
+    expect(testLogger.errorText, contains('STDOUT STUFF'));
   }, overrides: <Type, Generator>{
     FileSystem: () => fileSystem,
     ProcessManager: () => FakeProcessManager.list(<FakeCommand>[