[ffigen] Changes to support downstream clone

[liamappelbe]

An internal downstream clone needs to change the behavior of a few functions. This PR moves them all to a single overrideable_utils.dart file so that the clone can just swap out that file, rather than modifying the functions in place.

[github-actions]

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// Copyright (c) 2025, 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.

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Files
pkgs/jni/lib/src/third_party/generated_bindings.dart
pkgs/objective_c/lib/src/ns_input_stream.dart

[coveralls]

coverage: 85.395% (-0.001%) from 85.396%
when pulling b8cda69 on ffigen_upstream
into 0d57838 on main.

[dcharkes]

What about interface class PathHandler and class DefaultPathHandler in the main function? That way it's a single constructor call in the main function. And we we use a different main function downstream there is no need for a git patch at all. (This is how the patching for native assets in flutter tools in g3 works.)

[liamappelbe]

I'm pretty sure ffigen uses the same main function in g3 as it does externally, so I'd have to write a patch file either way

[dcharkes]

Aren't we importing overrideable_utils.dart in multiple places leading to multiple patches? Ah, you work around that by using an export of that file and never importing it anywhere else.

Other contributors to this project might easily autocomplete an import statement to overrideable_utils.dart which would then require another patch. So, if you want to go that route maybe add a @Deprecated() library; at the top to prevent contributors from ever importing this file anywhere.

[liamappelbe]

Done