MacOS build failure

[daniel-jasinski]

Build scripts use an explicit bash path as /usr/bin/bash, which fails on MacOS.
If all occurrences were replaced with /bin/bash, the project would be more portable.

[FoamScience]

I second this, also something like /bin/sh would be annoying in container environments
so we'll probably switch to the most portable version /usr/bin/env bash