Accept xz prebuilt archives

[macayu17]

Prerequisite

• Please consider implementing the feature as a hook script or plugin as a first step.
  • This updates the existing prebuilt-download updater.
• My PR addresses the following pyenv issue (if any)
  • Part of Provide prebuilt CPython for common environments pyenv#2334. It does not close the issue.

Description

• Here are some details about my PR
  • Allows pythons/update.sh to accept .tar.xz prebuilt archives while retaining .tar.gz support.
  • Updates the existing updater test to use the .tar.xz format produced by pyenv-binary.
  • Fixes the Update downloads failure in the binary publishing workflow.

Tests

• My PR adds the following unit tests (if any)
  • The updater test passes in a Linux container.
  • Both .tar.xz indexing and existing .tar.gz compatibility were checked.
  • ShellCheck and git diff --check pass.

---

Summary by cubic

Accepts .tar.xz prebuilt archives in pythons/update.sh while keeping .tar.gz support, fixing the binary publishing workflow's Update downloads failure. Updates the updater test to cover both archive formats.

^{Written for commit 4ee3a87. Summary will update on new commits.}

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.

[cubic-dev-ai]

All reported issues were addressed across 2 files

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>