Add --generate-hexfile flag to forc build for hex-encoded output

[JoE11-y]

close #5017

PR adds new --generate-hexfile flag to the forc build command, enabling it to output a hex-encoded JSON representation of the compiled binary alongside the .bin file.

✅ Changes

• Added --generate-hexfile flag to forc build.
• Outputs a .json file containing the hex-encoded script binary (e.g., contract-hex.json).
• Ensures bundler compatibility for frontend/SDK consumption.

🧪 Example Output

{
  "hex": "0xdeadbeefcafebabe..."
}

📦 Example Usage

forc build --generate-hexfile

Generates:

• contract.bin (as before)
• contract-hex.json (new hex representation)

Checklist

• I have linked to any relevant issues.
• I have commented my code, particularly in hard-to-understand areas.
• I have updated the documentation where relevant (API docs, the reference, and the Sway book).
  • If my change requires substantial documentation changes, I have requested support from the DevRel team
• I have added tests that prove my fix is effective or that my feature works.
• I have added (or requested a maintainer to add) the necessary Breaking* or New Feature labels where relevant.
• I have done my best to ensure that my PR adheres to the Fuel Labs Code Review Standards.
• I have requested a review from the relevant team or maintainers.

[fuel-cla-bot]

Thanks for the contribution! Before we can merge this, we need @JoE11-y to sign the Fuel Labs Contributor License Agreement.

[codspeed-hq]

CodSpeed Performance Report

Merging #7032 will not alter performance

_{Comparing JoE11-y:feat-add-generate-hex-flag (12862d9) with master (b59e1b6)}

Summary

✅ 22 untouched benchmarks

[zees-dev]

Few minor changes required:

• #[clap(long = "output-hexfile")]
• prepend output/ to hexfile to persist it there
• add back the empty line in .gitignore

Other than this; LGTM

[zees-dev]

minor fix to the hexfile some variant required

[zees-dev]

nice; thanks for this - LGTM 👍

[JoshuaBatty]

thanks for the PR