Pass EXCLUDED_ARCHS from Xcode project to xcodebuild for macOS builds (flutter#176948)

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Passes `EXCLUDED_ARCHS` from Xcode project build settings to the
xcodebuild command, fixing macOS builds when
  dependencies don't support all architectures.

  ### Problem
Release builds for macOS create universal binaries (arm64 + x86_64) by
default. This causes build failures when
using native dependencies that only provide binaries for a single
architecture. While developers can set
`EXCLUDED_ARCHS` in their Xcode project's xcconfig files, Swift Package
Manager dependencies don't respect this
  project-level setting.
  
  **Fixes**: flutter#176605

  ## Solution

Instead of adding a CLI flag, pass `EXCLUDED_ARCHS` from the Xcode
project's build settings directly to xcodebuild. This ensures Swift
Package Manager dependencies respect architecture exclusions set in the
project configuration.

**How it works:**
When `macos/Runner/Configs/Release.xcconfig` contains:
```xcconfig
EXCLUDED_ARCHS = x86_64
```

The build command now includes `EXCLUDED_ARCHS=x86_64`, creating an
arm64-only binary.

## Usage

**1. Edit your xcconfig file** (e.g.,
`macos/Runner/Configs/Release.xcconfig`):
```xcconfig
#include "../../Flutter/Flutter-Release.xcconfig"
#include "Warnings.xcconfig"

// Exclude x86_64 for dependencies that only support Apple Silicon
EXCLUDED_ARCHS = x86_64
```

**2. Build normally:**
```bash
flutter build macos --release
```

**Without exclusions (default behavior):**
```bash
# Creates universal binary (arm64 + x86_64)
flutter build macos --release
```

## Implementation

- Modified `buildMacOS()` to retrieve `EXCLUDED_ARCHS` from Xcode
project build settings
- Pass `EXCLUDED_ARCHS` to xcodebuild command when set and non-empty
- Removed unused `activeArch` parameter
- Added inline documentation explaining the SPM compatibility fix

## Testing

**Manual verification:**
- ✅ Built ExecuTorch Flutter example with `EXCLUDED_ARCHS = x86_64`:
arm64-only binary (518.6MB)
- ✅ Built without exclusions: universal binary (existing behavior)
- ✅ Verified architecture with `lipo -info`: arm64-only when excluded

**Unit tests:**
- ✅ Added test: "Passes EXCLUDED_ARCHS from Xcode project to xcodebuild
command"
- ✅ Added test: "Does not pass EXCLUDED_ARCHS when not set in Xcode
project"
- ✅ All 25 macOS build tests passing


*If you had to change anything in the [flutter/tests] repo, include a
link to the migration guide as per the [breaking change policy].*

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we expect every widget to implement].
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [x] All existing and new tests are passing.

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---------

Co-authored-by: Victoria Ashworth <15619084+vashworth@users.noreply.github.com>

Author: abdelaziz-mahdy

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

@@ -57,6 +57,7 @@ class BuildMacosCommand extends BuildSubCommand {
     if (!supported) {
       throwToolExit('"build macos" only supported on macOS hosts.');
     }
+
     await buildMacOS(
       flutterProject: project,
       buildInfo: buildInfo,

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

@@ -197,9 +197,21 @@ Future<void> buildMacOS({
     HostPlatform.darwin_x64 => 'x86_64',
     _ => throw UnimplementedError('Unsupported platform'),
   };
-  final String destination = buildInfo.isDebug
-      ? 'platform=${XcodeSdk.MacOSX.displayName},arch=$arch'
-      : XcodeSdk.MacOSX.genericPlatform;
+
+  // Determine the build destination
+  final String destination;
+  if (buildInfo.isDebug) {
+    // Debug builds default to current host architecture
+    destination = 'platform=${XcodeSdk.MacOSX.displayName},arch=$arch';
+  } else {
+    // Release builds default to universal binary
+    destination = XcodeSdk.MacOSX.genericPlatform;
+  }
+
+  // Get EXCLUDED_ARCHS from Xcode project build settings
+  // This allows developers to exclude specific architectures (e.g., x86_64)
+  // when dependencies don't support them
+  final String? excludedArches = buildSettings['EXCLUDED_ARCHS'];
 
   try {
     result = await globals.processUtils.stream(
@@ -223,6 +235,10 @@ Future<void> buildMacOS({
         'COMPILER_INDEX_STORE_ENABLE=NO',
         if (disabledSandboxEntitlementFile != null)
           'CODE_SIGN_ENTITLEMENTS=${disabledSandboxEntitlementFile.path}',
+        // Pass EXCLUDED_ARCHS from Xcode project to xcodebuild command
+        // This fixes Swift Package Manager not respecting EXCLUDED_ARCHS from the project
+        if (excludedArches != null && excludedArches.trim().isNotEmpty)
+          'EXCLUDED_ARCHS=$excludedArches',
         ...environmentVariablesAsXcodeBuildSettings(globals.platform),
       ],
       trace: true,

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

@@ -41,6 +41,28 @@ class FakeXcodeProjectInterpreterWithProfile extends FakeXcodeProjectInterpreter
   }
 }
 
+class FakeXcodeProjectInterpreterWithBuildSettings extends FakeXcodeProjectInterpreter {
+  FakeXcodeProjectInterpreterWithBuildSettings({this.overrides = const <String, String>{}});
+
+  final Map<String, String> overrides;
+
+  @override
+  Future<XcodeProjectInfo> getInfo(String projectPath, {String? projectFilename}) async {
+    return XcodeProjectInfo(<String>['Runner'], <String>['Debug', 'Release'], <String>[
+      'Runner',
+    ], BufferLogger.test());
+  }
+
+  @override
+  Future<Map<String, String>> getBuildSettings(
+    String projectPath, {
+    XcodeProjectBuildContext? buildContext,
+    Duration timeout = const Duration(minutes: 1),
+  }) async {
+    return <String, String>{...overrides, 'PRODUCT_BUNDLE_IDENTIFIER': 'com.example.test'};
+  }
+}
+
 final Platform macosPlatform = FakePlatform(
   operatingSystem: 'macos',
   environment: <String, String>{'FLUTTER_ROOT': '/', 'HOME': '/'},
@@ -85,6 +107,9 @@ void main() {
 
   // Sets up the minimal mock project files necessary for macOS builds to succeed.
   void createMinimalMockProjectFiles() {
+    fileSystem
+        .directory(fileSystem.path.join('macos', 'Runner.xcodeproj'))
+        .createSync(recursive: true);
     fileSystem
         .directory(fileSystem.path.join('macos', 'Runner.xcworkspace'))
         .createSync(recursive: true);
@@ -1010,4 +1035,92 @@ STDERR STUFF
       OperatingSystemUtils: () => FakeOperatingSystemUtils(hostPlatform: HostPlatform.darwin_x64),
     },
   );
+
+  testUsingContext(
+    'Passes EXCLUDED_ARCHS from Xcode project to xcodebuild command',
+    () async {
+      createMinimalMockProjectFiles();
+
+      fakeProcessManager.addCommands(<FakeCommand>[
+        setUpFakeXcodeBuildHandler(
+          'Release',
+          onRun: (_) {
+            fileSystem.file(fileSystem.path.join('macos', 'Flutter', 'ephemeral', '.app_filename'))
+              ..createSync(recursive: true)
+              ..writeAsStringSync('example.app');
+          },
+          additionalCommandArguments: <String>['EXCLUDED_ARCHS=x86_64'],
+        ),
+      ]);
+
+      final command = BuildCommand(
+        androidSdk: FakeAndroidSdk(),
+        buildSystem: TestBuildSystem.all(BuildResult(success: true)),
+        fileSystem: fileSystem,
+        logger: logger,
+        osUtils: FakeOperatingSystemUtils(),
+      );
+
+      await createTestCommandRunner(
+        command,
+      ).run(<String>['build', 'macos', '--release', '--no-pub']);
+
+      expect(fakeProcessManager, hasNoRemainingExpectations);
+    },
+    overrides: <Type, Generator>{
+      Platform: () => macosPlatform,
+      FileSystem: () => fileSystem,
+      ProcessManager: () => fakeProcessManager,
+      Pub: ThrowingPub.new,
+      FeatureFlags: () => TestFeatureFlags(isMacOSEnabled: true),
+      XcodeProjectInterpreter: () => FakeXcodeProjectInterpreterWithBuildSettings(
+        overrides: <String, String>{'EXCLUDED_ARCHS': 'x86_64'},
+      ),
+      OperatingSystemUtils: () => FakeOperatingSystemUtils(hostPlatform: HostPlatform.darwin_x64),
+    },
+  );
+
+  testUsingContext(
+    'Does not pass EXCLUDED_ARCHS when not set in Xcode project',
+    () async {
+      createMinimalMockProjectFiles();
+
+      fakeProcessManager.addCommands(<FakeCommand>[
+        setUpFakeXcodeBuildHandler(
+          'Release',
+          onRun: (_) {
+            fileSystem.file(fileSystem.path.join('macos', 'Flutter', 'ephemeral', '.app_filename'))
+              ..createSync(recursive: true)
+              ..writeAsStringSync('example.app');
+          },
+          // Note: No additionalCommandArguments - EXCLUDED_ARCHS should not be passed
+        ),
+      ]);
+
+      final command = BuildCommand(
+        androidSdk: FakeAndroidSdk(),
+        buildSystem: TestBuildSystem.all(BuildResult(success: true)),
+        fileSystem: fileSystem,
+        logger: logger,
+        osUtils: FakeOperatingSystemUtils(),
+      );
+
+      await createTestCommandRunner(
+        command,
+      ).run(<String>['build', 'macos', '--release', '--no-pub']);
+
+      expect(fakeProcessManager, hasNoRemainingExpectations);
+    },
+    overrides: <Type, Generator>{
+      Platform: () => macosPlatform,
+      FileSystem: () => fileSystem,
+      ProcessManager: () => fakeProcessManager,
+      Pub: ThrowingPub.new,
+      FeatureFlags: () => TestFeatureFlags(isMacOSEnabled: true),
+      XcodeProjectInterpreter: () => FakeXcodeProjectInterpreterWithBuildSettings(
+        // Empty overrides - no EXCLUDED_ARCHS
+      ),
+      OperatingSystemUtils: () => FakeOperatingSystemUtils(hostPlatform: HostPlatform.darwin_x64),
+    },
+  );
 }