Function get_upgradable_packages 

pub fn get_upgradable_packages() -> HashSet<String>

What: Collect names of packages that have upgrades available via pacman.

Inputs:

• (none): Reads upgrade information by invoking pacman -Qu.

Output:

• Returns a set containing package names that pacman reports as upgradable.

Details:

• Trims each line from the command output and extracts the leading package token before version metadata.
• Gracefully handles command failures by returning an empty set to avoid blocking dependency checks.