Switch all MacOS scripts to use GNU utils

[nikola-matic]

We generally have to tend subtle issues with GNU vs BSD tooling (find, grep, etc.), as we write most of our scripts for Linux, and expect them to work on Macs; however, Mac uses BSD tooling, whereas Linux used GNU, and as there are differences between GNU and BSD implementations, we should switch all of our scripts that will potentially be run on a Macintosh machine to make sure GNU grep is installed and used.

An example of such an issue is the check style script, which does not run properly on Mac due to differences in grep.
#13492