hardcode kustomize download to bypass github api rate limits

[trdoyle81]

What type of PR is this?
/kind failing-test

What does this PR do / why we need it:
Fixes flaky OpenShift CI images job failures.

The install_kustomize.sh script in the CI Dockerfile queries the GitHub API, which frequently gets blocked by rate limits (403 API Rate Limit Exceeded) due to shared CI IPs. This causes a silent download failure and crashes the build during the tar extraction. This PR replaces the script with a direct curl | tar download of Kustomize v5.8.1. This bypasses the GitHub API completely and makes the CI build deterministic.

Have you updated the necessary documentation?

• Documentation update is required by this PR.
• Documentation has been updated.

Which issue(s) this PR fixes:

Fixes #

Test acceptance criteria:

• Unit Test
• E2E Test

How to test changes / Special notes to the reviewer:
podman build -t ci-test .

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository YAML (base), Organization UI (inherited)

Review profile: CHILL

Plan: Enterprise

Run ID: 8028953a-6bec-47a6-b9ee-f686db564f94

📥 Commits

Reviewing files that changed from the base of the PR and between b008a14 and 4d1bbe8.

📒 Files selected for processing (1)

• openshift-ci/build-root/Dockerfile

🔗 Linked repositories identified

CodeRabbit considers these linked repositories for cross-repo context during reviews:

• argoproj-labs/argocd-operator (manual)

🚧 Files skipped from review as they are similar to previous changes (1)

• openshift-ci/build-root/Dockerfile

---

📝 Walkthrough

Summary by CodeRabbit

Release Notes

• Chores
  • Improved the build environment’s Kustomize installation to use a pinned, versioned release artifact instead of running an upstream installer script.
  • Added checksum verification during installation to improve integrity and reproducibility.
  • Set the default Kustomize version to v5.8.1 and allow overriding it when needed.

Walkthrough

The Dockerfile adds build arguments for the Kustomize version and checksum, then replaces the script-based install with a checksum-verified tarball download and extraction into /usr/local/bin.

Changes

Kustomize Installation Versioning

Layer / File(s)	Summary
Kustomize version argument and direct installation openshift-ci/build-root/Dockerfile	Adds KUSTOMIZE_VERSION and KUSTOMIZE_SHA256, then downloads, verifies, extracts, and removes the versioned Kustomize release tarball.

Estimated code review effort: 2 (Simple) | ~8 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly describes the main change: hardcoding the Kustomize download to avoid GitHub API rate limits.
Description check	✅ Passed	The description accurately explains the CI failure, the Kustomize download change, and the testing done.
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.

---

_{Comment @coderabbitai help to get the list of available commands.}

[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@openshift-ci/build-root/Dockerfile`:
- Line 18: The Dockerfile currently downloads and installs kustomize using the
RUN curl ... | tar -xz pipeline with KUSTOMIZE_VERSION but performs no integrity
check; update the Dockerfile to fetch the corresponding release checksum or
signature for kustomize (using KUSTOMIZE_VERSION), verify the downloaded archive
before extracting (e.g., compare sha256/sha512 against the release checksum or
verify a GPG signature), and only copy the binary to /usr/local/bin if the
verification succeeds; reference the existing KUSTOMIZE_VERSION variable and the
kustomize_${KUSTOMIZE_VERSION}_linux_amd64.tar.gz artifact when implementing the
checksum/sig retrieval and verification step.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Enterprise

Run ID: 8d9e56c1-8ad1-4b23-adc2-2ac0b82e005b

📥 Commits

Reviewing files that changed from the base of the PR and between 949f348 and b008a14.

📒 Files selected for processing (1)

• openshift-ci/build-root/Dockerfile

[svghadi]

/lgtm

[trdoyle81]

/retest

[trdoyle81]

/retest

[svghadi]

/lgtm
/approve

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: svghadi

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Details

Needs approval from an approver in each of these files:

• openshift-ci/build-root/OWNERS [svghadi]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[openshift-ci]

@trdoyle81: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/v4.14-kuttl-sequential	4d1bbe8	link	false	/test v4.14-kuttl-sequential

Full PR test history. Your PR dashboard.

Details

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository. I understand the commands that are listed here.

[trdoyle81]

/retest