Xcode build phase script improvements

[IodaMikeMapbox]

Description

Our build phase has a script for copying frameworks, that script has a room for improvements, for now we noticed. At least:

• use set -euo pipefail as a general setup;
• check presence of arguments if it's required;
• add comprehensive comments, because for now it's not clear at first sight what is going on;
• etc.

More useful notes about script improvements can be found in the pr.

Goal

Improve xcode build phase script.

Steps

• Improve the script;
• Tested and acceptance criteria is matched (result matches the goal).