Improve iOS unpack target's error messages (flutter#154649)

Improves the formatting and error messages of the target that unpacks the Flutter framework in Flutter iOS builds.

Follow up to: flutter#154645
Part of flutter#151567

Author: loic-sharma

packages/flutter_tools/lib/src/build_system/targets/ios.dart

@@ -258,19 +258,20 @@ abstract class UnpackIOS extends Target {
 
   @override
   List<Source> get inputs => <Source>[
-        const Source.pattern(
-            '{FLUTTER_ROOT}/packages/flutter_tools/lib/src/build_system/targets/ios.dart'),
-        Source.artifact(
-          Artifact.flutterXcframework,
-          platform: TargetPlatform.ios,
-          mode: buildMode,
-        ),
-      ];
+    const Source.pattern(
+      '{FLUTTER_ROOT}/packages/flutter_tools/lib/src/build_system/targets/ios.dart',
+    ),
+    Source.artifact(
+      Artifact.flutterXcframework,
+      platform: TargetPlatform.ios,
+      mode: buildMode,
+    ),
+  ];
 
   @override
   List<Source> get outputs => const <Source>[
-        Source.pattern('{OUTPUT_DIR}/Flutter.framework/Flutter'),
-      ];
+    Source.pattern('{OUTPUT_DIR}/Flutter.framework/Flutter'),
+  ];
 
   @override
   List<Target> get dependencies => <Target>[];
@@ -377,7 +378,12 @@ abstract class UnpackIOS extends Target {
     ]);
 
     if (verifyResult.exitCode != 0) {
-      throw Exception('Binary $frameworkBinaryPath does not contain $archs. Running lipo -info:\n$lipoInfo');
+      throw Exception(
+        'Binary $frameworkBinaryPath does not contain architectures "$archs".\n'
+        '\n'
+        'lipo -info:\n'
+        '$lipoInfo',
+      );
     }
 
     // Skip thinning for non-fat executables.
@@ -400,7 +406,14 @@ abstract class UnpackIOS extends Target {
     ]);
 
     if (extractResult.exitCode != 0) {
-      throw Exception('Failed to extract $archs for $frameworkBinaryPath.\n${extractResult.stderr}\nRunning lipo -info:\n$lipoInfo');
+      throw Exception(
+        'Failed to extract architectures "$archs" for $frameworkBinaryPath.\n'
+        '\n'
+        'stderr:\n'
+        '${extractResult.stderr}\n\n'
+        'lipo -info:\n'
+        '$lipoInfo',
+      );
     }
   }
 }

packages/flutter_tools/test/general.shard/build_system/targets/ios_test.dart

@@ -20,7 +20,10 @@ import '../../../src/context.dart';
 import '../../../src/fake_process_manager.dart';
 import '../../../src/fakes.dart';
 
-final Platform macPlatform = FakePlatform(operatingSystem: 'macos', environment: <String, String>{});
+final Platform macPlatform = FakePlatform(
+  operatingSystem: 'macos',
+  environment: <String, String>{},
+);
 
 const List<String> _kSharedConfig = <String>[
   '-dynamiclib',
@@ -715,7 +718,7 @@ void main() {
         fileSystem: fileSystem,
         outputDir: outputDir,
         defines: <String, String>{
-          kIosArchs: 'arm64 armv7',
+          kIosArchs: 'arm64 x86_64',
           kSdkRoot: 'path/to/iPhoneOS.sdk',
         },
       );
@@ -732,7 +735,7 @@ void main() {
           binary.path,
           '-verify_arch',
           'arm64',
-          'armv7',
+          'x86_64',
         ], exitCode: 1),
       ]);
 
@@ -741,7 +744,10 @@ void main() {
         throwsA(isException.having(
           (Exception exception) => exception.toString(),
           'description',
-          contains('does not contain arm64 armv7. Running lipo -info:\nArchitectures in the fat file:'),
+          contains(
+            'does not contain architectures "arm64 x86_64".\n\n'
+            'lipo -info:\nArchitectures in the fat file:',
+          ),
         )),
       );
     });
@@ -757,7 +763,7 @@ void main() {
         fileSystem: fileSystem,
         outputDir: outputDir,
         defines: <String, String>{
-          kIosArchs: 'arm64 armv7',
+          kIosArchs: 'arm64 x86_64',
           kSdkRoot: 'path/to/iPhoneOS.sdk',
         },
       );
@@ -774,7 +780,7 @@ void main() {
           binary.path,
           '-verify_arch',
           'arm64',
-          'armv7',
+          'x86_64',
         ]),
         FakeCommand(command: <String>[
           'lipo',
@@ -783,7 +789,7 @@ void main() {
           '-extract',
           'arm64',
           '-extract',
-          'armv7',
+          'x86_64',
           binary.path,
         ], exitCode: 1,
         stderr: 'lipo error'),
@@ -794,7 +800,12 @@ void main() {
         throwsA(isException.having(
           (Exception exception) => exception.toString(),
           'description',
-          contains('Failed to extract arm64 armv7 for output/Flutter.framework/Flutter.\nlipo error\nRunning lipo -info:\nArchitectures in the fat file:'),
+          contains(
+            'Failed to extract architectures "arm64 x86_64" for output/Flutter.framework/Flutter.\n\n'
+            'stderr:\n'
+            'lipo error\n\n'
+            'lipo -info:\nArchitectures in the fat file:',
+          ),
         )),
       );
     });
@@ -840,7 +851,7 @@ void main() {
         fileSystem: fileSystem,
         outputDir: outputDir,
         defines: <String, String>{
-          kIosArchs: 'arm64 armv7',
+          kIosArchs: 'arm64 x86_64',
           kSdkRoot: 'path/to/iPhoneOS.sdk',
         },
       );
@@ -857,7 +868,7 @@ void main() {
           binary.path,
           '-verify_arch',
           'arm64',
-          'armv7',
+          'x86_64',
         ]),
         FakeCommand(command: <String>[
           'lipo',
@@ -866,7 +877,7 @@ void main() {
           '-extract',
           'arm64',
           '-extract',
-          'armv7',
+          'x86_64',
           binary.path,
         ]),
         xattrCommand,