Update shell scripts

[wiryhatbox]

• Safer scripts with set -euf and other options whenever possible

• Make scripts more portable

• Quote variables

• Use end-of-options (--) to make scripts safer

• Use either curl or wget with safer parameters

• All commands (even mkdir/cd) exit properly on failure

• Rethink eval arguments

[wiryhatbox]

Let me know if you need help with the review, functionality remained unchanged.

[umerbutt007]

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