Switch all MacOS scripts to use GNU utils

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`.
https://github.com/ethereum/solidity/issues/13492

Start by reviewing the check style script mentioned in the issue and the related issue #13492, then inventory scripts that may run on macOS and use tools such as grep or find. Determine how GNU grep should be installed and selected; done means the affected scripts use GNU utilities and work on macOS without the reported BSD/GNU differences.

Written by the indexing model from the issue text.