SG-33500 Cleanup build_resources.sh scripts

[julien-lang]

• Replicate change from 8d116c7c
• Remove useless mogrify command since #984
• Make the sed command work with both GNU sed (Linux) and BSD sed (macOS)
• Remove useless UI_PYTHON_PATH variable

Related to #977. I'm not sure that we will merge this one but I wanted to point out what is wrong with the current script.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 79.44%. Comparing base (a3f5bc0) to head (cc3b75b).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #984 +/- ## ======================================= Coverage 79.44% 79.44% ======================================= Files 199 199 Lines 20851 20851 ======================================= Hits 16566 16566 Misses 4285 4285 ```

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[julien-lang]

Unnecessary changes