utils/gems: run setup_gem_environment!

[cho-m]

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This was previously done by install_bundler! before d562e44

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I don't know about other places we were running install_bundler! but the removal of this at below (originally line 244) seems to cause issues:

• d562e44#diff-a1a5395d198aee1fb8c45c74bf9dd49ef5734887a17ee84000badc7d58b82e98L244

Prior to change, strange errors like

• if brew Ruby is installed and on PATH, gems link to that one. Need to purge old gems to get brew to work again.
• brew tries running on system Ruby 2

[Copilot]

Pull Request Overview

This PR restores the setup_gem_environment! call that was removed in a previous commit (d562e44), ensuring it runs for all invocations of install_bundler_gems!, not just during tests. The change also simplifies the conditional logic by using an early return pattern.

Key Changes:

• Moved setup_gem_environment! call outside the test-only conditional block
• Refactored the test environment check to use an early return pattern
• Ensures gem environment is properly configured before the early return in test mode

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[p-linnane]

Thanks @cho-m. Looks like this worked: https://github.com/Homebrew/homebrew-core/actions/runs/19355010357/job/55374526314

[MikeMcQuaid]

Makes sense, thanks @cho-m!