build-utils.sh is responsible for filling these variables.
Note: getversion.sh and getversion.bat are still currently used by
meson. gettier is no longer used with these changes.
The name json.hpp conflicts with the JSON for Modern C++ library that
is also used by Developer. Renames json.hpp and json.cpp to jsonpp.hpp
and jsonpp.cpp aka "JSON Pretty Printer".
Fixes up scripts (except under /linux) to use `#!/usr/bin/env bash`
instead of `#!/bin/bash` or `#!/bin/sh` so that we don't end up with
the ancient version of bash supplied with macOS.
This became urgent with this PR, because of bash-4.xisms in
build-utils.sh, for example on line 572:
```
if [[ -v _builder_params[$e] ]]; then
```
