Use aria2c download tool by default on package download if available in
the system.
aria2c permits to use multiple mirrors and may improve download speed on
special context where servers are hard to reach.
Co-authored-by: Christian Marangi <ansuelsmth@gmail.com>
Signed-off-by: Bradford Zhang <zyc@zyc.name>
[ fix wrong var in the script and improve commit description ]
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
