Mach-O image writer

Issue: https://github.com/dart-lang/sdk/issues/61635
Change-Id: I05b9834d0427b3959f8cefce68a9a084b73eb8c8
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/475406
Reviewed-by: Slava Egorov <vegorov@google.com>
Commit-Queue: Alexander Markov <alexmarkov@google.com>

pkg/native_compiler/lib/snapshot/image_writer.dart

@@ -0,0 +1,11 @@
+// Copyright (c) 2026, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:typed_data';
+
+abstract base class ImageWriter {
+  int addInstructions(Uint8List instructions);
+  int addReadOnlyData(List<Uint8List> data, int length);
+  void writeTo(Sink<List<int>> out);
+}

pkg/native_compiler/pubspec.yaml

@@ -11,6 +11,7 @@ resolution: workspace
 # Use 'any' constraints here; we get our versions from the DEPS file.
 dependencies:
   cfg: any
+  crypto: any
   kernel: any
 
 dev_dependencies: