etcd 3.4: install shellcheck and report if not installed.

[thedtripp]

Looking into https://github.com/etcd-io/etcd/issues/17472, it appears that shellcheck is not installed. I added some code to install it, though I'm not sure if this is the correct place to do this.

At the very least, I think we should add an else block to inform that shellcheck isn't installed:

if command -v shellcheck >/dev/null; then
    shellcheckResult=$(shellcheck -fgcc build test scripts/*.sh 2>&1 || true)
    if [ -n "${shellcheckResult}" ]; then
        echo -e "shellcheck checking failed:\\n${shellcheckResult}"
        exit 255
    fi
else
    echo "Skipping shellcheck..."
fi

[k8s-ci-robot]

Hi @thedtripp. Thanks for your PR.

I'm waiting for a etcd-io member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[idnandre]

Hi @thedtripp @jmhbnz. In "Tests / test (linux-amd64-fmt)" workflows there is still exists skipping revive message. Are we need to install revive also?

[thedtripp]

Hey @thedtripp - Thanks for proposing this, agree shellcheck should be automatically installed if not already present.

We do already have this functionality in main, refer: #14872.

We should backport the approach from that pull request to release-3.5 then release-3.4 so all branches managed shellcheck the same way.

Hey @jmhbnz. I submitted another PR for 3.5 here: https://github.com/etcd-io/etcd/pull/18229 If it looks good, I will repeat for 3.4. Thanks.

[thedtripp]

Hi @thedtripp @jmhbnz. In "Tests / test (linux-amd64-fmt)" workflows there is still exists skipping revive message. Are we need to install revive also?

Hey @idnandre, Thanks for your review. I plan to address revive in a separate PR.

[jmhbnz]

Closing in favor of #18248