[native_assets_builder] Fix hook compile caching

[dcharkes]

The package_config.json can update with irrelevant information (such as the timestamp). Don't recompile the hooks if only the timestamp changed.

Testing: The existing tests started failing. Possibly after dartdev started running pub get more often automatically after https://dart-review.googlesource.com/c/sdk/+/404583.

[github-actions]

Package publishing

Package	Version	Status	Publish tag (post-merge)
package:native_assets_builder	0.11.1	ready to publish	native_assets_builder-v0.11.1
package:ffi	2.1.3	already published at pub.dev
package:ffigen	17.0.0-wip	WIP (no publish necessary)
package:jni	0.14.0-wip	WIP (no publish necessary)
package:jnigen	0.13.1	already published at pub.dev
package:native_assets_cli	0.11.0	already published at pub.dev
package:native_toolchain_c	0.8.0	already published at pub.dev
package:objective_c	5.0.0-wip	WIP (no publish necessary)
package:swift2objc	0.0.1-wip	WIP (no publish necessary)
package:swiftgen	0.0.1-wip	WIP (no publish necessary)

Documentation at https://github.com/dart-lang/ecosystem/wiki/Publishing-automation.

[github-actions]

PR Health

Breaking changes ✔️

Package	Change	Current Version	New Version	Needed Version	Looking good?
native_assets_builder	None	0.11.0	0.11.1	0.11.0	✔️

Changelog Entry ✔️

Package	Changed Files

Changes to files need to be accounted for in their respective changelogs.

API leaks ✔️

The following packages contain symbols visible in the public API, but not exported by the library. Export these symbols or remove them from your publicly visible API.

Package	Leaked API symbols

License Headers ✔️

// 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.

Files
no missing headers

All source files should start with a license header.

Unrelated files missing license headers

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

[coveralls]

coverage: 88.64% (+0.04%) from 88.604%
when pulling c61512d on package-config-timestamp
into ca5f3d2 on main.