formula_creator: add deny network for ruby

[cho-m]

Examples for handling network access of Ruby formulae at:

• various(ruby dependents): add deny_network_access! homebrew-core#302225

Based on https://guides.rubygems.org/caching-and-vendoring/

Some extra notes:

• Using bundle config to preserve config across both fetch & build phase. Could consider making this part of superenv / build environment, but would need to check on usage (and will need a way to avoid for stuff like sorbet-static which currently uses prebuilt binaries)
• BUNDLE_PATH=.bundle is Bundler 5 default so can be removed in the future. Currently needed as RubyGems still creates some bin files for main package even when --no-install is used.

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[Copilot]

🟢 Approval recommended

The implementation matches the staged fetch/build lifecycle and includes focused template coverage.

Pull request overview

Updates Ruby formula templates to support network-isolated builds.

Changes:

• Cache Bundler dependencies during fetch.
• Install cached gems locally with network access denied.
• Add template-generation coverage for Ruby mode.

File summaries

File	Description
Library/Homebrew/formula_creator.rb	Adds offline Ruby dependency handling.
Library/Homebrew/test/formula_creator_spec.rb	Verifies generated Ruby templates.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 0
• Review effort level: Balanced

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[MikeMcQuaid]

Lovely!

[MikeMcQuaid]

Follow-up: wonder if we can/should use default env instead for any of these.

[cho-m]

version and without are probably safe.

force_ruby_platform does break some packages that only provide native gems. Main one is sorbet-static which currently impacts ruby-lsp.

Though it may be better to require formula to configure the inverse so that it is more obvious when a prebuilt is used:

system "bundle", "config", "set", "force_ruby_platform", "false"

EDIT: for ruby-lsp, I think it doesn't actually need sorbet-static but Bundler/RubyGem limitation requires resolving development dependencies even when we set without. We also hit this in brew.

[MikeMcQuaid]

Though it may be better to require formula to configure the inverse so that it is more obvious when a prebuilt is used:

Good idea 👍🏻