CI: pass SHLVL to make ~ubuntu/.bash_logout succeed

[aramprice]

NOTE: this repository uses a "Merge Forward" strategy

Changes should be made in the earliest applicable branch, and
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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: d0a4be4e-87de-47b6-8957-9cae6ff7003b

📥 Commits

Reviewing files that changed from the base of the PR and between 21f4272 and e045098.

📒 Files selected for processing (2)

• ci/tasks/build.sh
• ci/tasks/os-images/build.sh

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Walkthrough

This PR updates two CI build scripts (ci/tasks/build.sh and ci/tasks/os-images/build.sh) to add SHLVL to the sudo --preserve-env list used in heredoc invocations and to remove the interactive -i flag from /bin/bash --login. Comments were added noting that forwarding SHLVL prevents ~ubuntu/.bash_logout from causing the session to exit.

Suggested reviewers

• mkocher
• ragaskar
• rkoster

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title directly relates to the main change: preserving the SHLVL environment variable in CI build scripts to resolve bash_logout issues.
Description check	✅ Passed	The description matches the provided template exactly, documenting the repository's Merge Forward strategy and workflow steps.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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• Commit unit tests in branch fix-sudo-env

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[Copilot]

Pull request overview

Updates the CI task wrappers that sudo to the ubuntu user so the login shell exits cleanly by preserving SHLVL in the environment, avoiding failures triggered by ~ubuntu/.bash_logout.

Changes:

• Preserve SHLVL in sudo --preserve-env for the ubuntu subshell used to run bundle/rake.
• Switch the ubuntu subshell invocation from bash --login -i to bash --login.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
ci/tasks/os-images/build.sh	Preserve SHLVL for the ubuntu login shell used to build OS images; drop interactive bash flag.
ci/tasks/build.sh	Preserve SHLVL for the ubuntu login shell used to build stemcells; drop interactive bash flag.

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