Replace 'x-hack' in extensions and lib/functions/artifacts files

[sweep-nightly[bot]]

Description

This PR replaces the outdated 'x-hack' shell scripting practice with a modern approach in the specified files. The 'x-hack' was used to ensure compatibility across different shells and systems, but it is now obsolete. The replacement involves removing the 'x' prefix from the variable and the value in the comparison. This update improves the codebase by using a more reliable and simplified approach.

Summary of Changes

• Replaced 'x-hack' with a modern approach in the following files:
  • extensions/nvidia.sh
  • extensions/v4l2loopback-dkms.sh
  • extensions/grub.sh
  • extensions/nomod.sh
  • extensions/zfs.sh
  • lib/functions/artifacts/artifact-armbian-bsp-cli.sh
  • lib/functions/artifacts/artifact-firmware.sh
  • lib/functions/artifacts/artifacts-obtain.sh

Please review and merge this PR to improve the codebase and ensure compatibility with modern shell scripting practices.

Fixes #96.

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