Make commit-code-check.sh POSIX compatible

Problem/Motivation

meantime core/scripts/dev/commit-code-check.sh script requires bash to be executed but there's not a lot of bashisms involved so could be cleaned

Steps to reproduce

for example conditions using [[ ]]

Proposed resolution

replace all bash-specific places with POSIX compatible approach, ref https://mywiki.wooledge.org/Bashism

Remaining tasks

patch/review/commit

User interface changes

API changes

Data model changes

Release notes snippet