[UI] - Adding logic to enable init.sh execution on Alpine Linux

[izaac]

Summary

First part of rancher/qa-tasks#1549

Occurred changes and/or fixed issues

Adding logic to execute the Jenkins CI initialization script on Alpine Linux images. This allows the execution on the new runners.
Explicitly set the GOROOT to the downloaded golang extracted tar.
Everything else is shell agnostic and runs transparently in then ash shell.

Technical notes summary

Alpine Linux isn't binary compatible by default with the golang Linux binaries as it ships with the C lib musl. The go binaries require glibc. Adding gcompat fix this.

Areas or cases that should be tested

Jenkins

Checklist

• The PR is linked to an issue and the linked issue has a Milestone, or no issue is needed
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• The PR has automated tests or clear instructions for manual tests and the linked issue has appropriate QA labels, or tests are not needed
• The PR has reviewed with UX and tested in light and dark mode, or there are no UX changes