build.rs ignores the rust_release parameter

[codercengiz]

Describe the bug

If we want to use rust_release parameter with build.rs ,
cargo build generates without considering frb attributes. For example, even if you specify #[cfg_attr(feature = "mobile",frb(sync))], it generates async function. However, flutter_rust_bridge_codegen generate generates as expected.

The two method are generating different codes.

Steps to reproduce

1. Download the simple app https://github.com/codercengiz/frb_test/
2. Go to rust folder and run cargo build then you will see on generated file lib/src/rust/api/simple.dart

Future<String> greet({required String name}) =>
    RustLib.instance.api.crateApiSimpleGreet(name: name);

3. To compare this generated code with the generated codes by codegen
   Install the codegen from git on master branch cargo install --git https://github.com/fzyzcjy/flutter_rust_bridge --branch master flutter_rust_bridge_codegen
4. run flutter_rust_bridge_codegen generate, then you will see on generated file lib/src/rust/api/simple.dart

String greet({required String name}) =>
    RustLib.instance.api.crateApiSimpleGreet(name: name);

Logs

❯ flutter_rust_bridge_codegen --version
flutter_rust_bridge_codegen 2.4.0

Expected behavior

No response

Generated binding code

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OS

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Version of flutter_rust_bridge_codegen

No response

Flutter info

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Version of clang++

No response

Additional context

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