archlinux: Add missing system packages (arch.txt), add arch section to installation manual, fix detection of system packages #29366
Description
https://groups.google.com/d/msg/sage-devel/JgArPVx7dwg/gMxeB4b7AgAJ
To test:
tox -e docker-archlinux-latest-standard
CC: @videlec @antonio-rojas @dimpase
Component: porting
Author: Matthias Koeppe, Vincent Delecroix
Branch/Commit: 338468f
Reviewer: Dima Pasechnik
Issue created by migration from https://trac.sagemath.org/ticket/29366