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
```
When working on a new build script, I tripped over the `-?` question
mark help parameter here, as it needs to be escaped. Opted to fix all
the instances in our scripts, although AFAICT there would not have been
current bugs arising from this, as there were no conflicting one
character options lower in the case list.
* Update FV build to download nrc.str.sencoten.model.kmp
* Update FV app to install the model
* Rebuild active keyboards list using keyboard info from kmp.json
Follow-on to #3300
* Update the FV Android app to use the same build script to download its default keyboard package. (fv_all.kmp)
* This means downloading fv_all.kmp is the only valid option for the build (remove option to copy/rebuild keyboards)
* Reduce the number of exports in the Bash scripts
* Also removes sil_euro_latin.kmp since the app will fallback to fv_all/sil_euro_latin (in a future PR)
Incorporate changes from #3040 into oem/firstvoices/common/build_keyboards.sh
I had to include sil_euro_latin.kmp because KMManager reverts to default package ID (sil_euro_latin) on KMW exceptions.
This will also need a keyboards build of fv_all.kmp (next version 12.2 should include touch keyboards)
