Remove linux-x64 unpack logic (#42962)

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

@@ -31,15 +31,6 @@ const Map<TargetPlatform, List<String>> artifactFilesByPlatform = <TargetPlatfor
     'icudtl.dat',
     'cpp_client_wrapper/',
   ],
-  TargetPlatform.linux_x64: <String>[
-    'libflutter_linux_glfw.so',
-    'flutter_export.h',
-    'flutter_messenger.h',
-    'flutter_plugin_registrar.h',
-    'flutter_glfw.h',
-    'icudtl.dat',
-    'cpp_client_wrapper_glfw/',
-  ]
 };
 
 /// Copies desktop artifacts to local cache directories.
@@ -54,7 +45,7 @@ class UnpackCommand extends FlutterCommand {
   }
 
   @override
-  String get description => 'unpack desktop artifacts';
+  String get description => '(DEPRECATED) unpack desktop artifacts';
 
   @override
   String get name => 'unpack';
@@ -130,8 +121,7 @@ class ArtifactUnpacker {
         cacheStamp = 'windows-sdk';
         break;
       case TargetPlatform.linux_x64:
-        cacheStamp = 'linux-sdk';
-        break;
+        return true;
       default:
         throwToolExit('Unsupported target platform: $platform');
     }

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

+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter_tools/src/cache.dart';
+import 'package:flutter_tools/src/commands/unpack.dart';
+
+import '../../src/common.dart';
+import '../../src/mocks.dart';
+import '../../src/testbed.dart';
+
+void main() {
+  Testbed testbed;
+
+  setUpAll(() {
+    Cache.disableLocking();
+  });
+
+  tearDownAll(() {
+    Cache.enableLocking();
+  });
+
+  setUp(() {
+    testbed = Testbed();
+  });
+
+  test('Returns success for linux unconditionally', () => testbed.run(() async {
+    final UnpackCommand unpackCommand = UnpackCommand();
+    applyMocksToCommand(unpackCommand);
+
+    await createTestCommandRunner(unpackCommand).run(
+      <String>[
+        'unpack',
+        '--cache-dir=foo',
+        '--target-platform=linux-x64',
+      ],
+    );
+  }));
+}