Merge #1917

1917: Update Alpine version from 3.10 to 3.14 build_arm.sh r=mergify[bot] a=Erriez

## What type of PR?

Update Alpine version from 3.10 to 3.14 in `build_arm.sh` script.

## What does this PR do?

### Related issue(s)
- Mention an issue like: #1200

## Prerequistes
Before we can consider review and merge, please make sure the following list is done and checked.
If an entry in not applicable, you can check it or remove it from the list.

- [ ] In case of feature or enhancement: documentation updated accordingly
- [ ] Unless it's docs or a minor change: add [changelog](https://mailu.io/master/contributors/workflow.html#changelog) entry file.

Co-authored-by: Erriez <Erriez@users.noreply.github.com>

tests/build_arm.sh

@@ -1,6 +1,6 @@
 #!/bin/bash -x
 
-ALPINE_VER="3.10"
+ALPINE_VER="3.14"
 DISTRO="balenalib/rpi-alpine:$ALPINE_VER"
 # Used for webmails
 QEMU="arm"