Fix call toolchain version with fvm support

[SirKrlos]

Changes

Fix call dart/flutter toolchain --version with fvm support.

Checklist

• An issue to be fixed by this PR is listed above.
• New tests are added to ensure new features are working. Please refer to this page to see how to add a test.
• ./frb_internal precommit --mode slow (or fast) is run (it internal runs code generator, does auto formatting, etc).
• If this PR adds/changes features, documentations (in the ./website folder) are updated.
• CI is passing. Please refer to this page to see how to solve a failed CI.

Remark for PR creator

• ./frb_internal --help shows utilities for development.
• If fzyzcjy does not reply for a few days, maybe he just did not see it, so please ping him.

[welcome]

Hi! Thanks for opening this pull request! 😄

[SirKrlos]

Test performed in an environment with only the installed fvm, without the global version of the Flutter in the system.

Preview of error before the correction below:
$ flutter_rust_bridge_codegen generate
[2024-11-06T07: 52: 38.764Z WARN /home/usertest/.cargo/registry/src/index.crates.io-6f17d22bba15001f/flutter_rust_bridge_codegen-2.6.0/src/library/commands/command_runner.rs:153] command="sh" "-c" ""flutter" "--version"" stdout= stderr=sh: linha 1: flutter: command not found
Error: Dart/Flutter Toolchain Not Available

Preview of the result after correction:
$ flutter_rust_bridge_codegen generate
[2.0s] Parse ⠂
└── [2.1s] Cargo expand & syn parse ⠄

[fzyzcjy]

Great job!

[welcome]

Hi! Congrats on merging your first pull request! 🎉

[fzyzcjy]

@all-contributors please add @SirKrlos for code

[allcontributors]

@fzyzcjy

I've put up a pull request to add @SirKrlos! 🎉