Update build_cross.sh

[notsatan]

Convert the bash script to be more responsive and terminal-friendly, generate a checksums.txt file when done. Archive the contents into zip/gz container(s) if possible.

While the original idea to make this script was inspired from this repository, the script is my own implementation with minor tweaks.

How to run this script:

bash ./build_cross.sh <version-number>

The version number argument is not required, but certainly would make the output files look better if added

Features:

• Generate build(s) for multiple targets
• Terminal-friendly output
• Archive the files in .gz/.zip containers (if possible)
• Generate a text file containing check-sums when done

[notsatan]

Here's a GIF on how the script looks like while working