Makefile:
Move shellcheck commands from .gitlab-ci.yml.

.gitlab-ci.yml:
Run `make check`.
Prevent partial upgrades, i.e. use '-Syu'.
Prevent reinstalling already installed packages by using pacman's '--needed' option.
Don't force-download the package database.

When one calls the `build.sh` scripts with bash instead of the shebang
`$script_path` contains the filepath, not the parent dir:

```
% cd /path
% grep -A2 script_path= build.sh
script_path=$(readlink -f "${0%/*}")
echo "$script_path"
exit 0
% ./build.sh
/path
% bash build.sh
/path/build.sh
```

This commit fixes that:

```
% grep -A2 script_path= build.sh
script_path="$( cd -P "$( dirname "$(readlink -f "$0")" )" && pwd )"
echo "$script_path"
exit 0
% ./build.sh
/path
% bash build.sh
/path
```

linux only gets pulled in because of broadcom-wl and mkinitcpio (usually) gets pulled in by linux.

Move all required packages to packages.x86_64.
Test file availability before copying them.

archiso/initcpio/install/*:
Setting bash shebang for all scripts and making them comform with shellcheck.

archiso/initcpio/{hooks,script}/*:
Setting ash shebang for all scripts and making them comform with shellcheck (for dash, as shellcheck has no ash specific
ruleset). Essentially the ash based scripts should be POSIX compliant as much as possible to have an easier time
writing, debugging and maintaining them.
Ensuring that variables are not treated as options and introducing variable quoting.

.gitlab-ci.yml:
Integrating shellcheck for initcpio scripts.

Closes #32

/usr/local/bin/Installation_guide:
Add a convenience script which opens the installation guide in lynx.

/etc/motd:
Provide a message with minimal instructions for connecting to internet and inform about the Installation_guide convenience script.

dialog was only added because it was needed for netctl's wifi-menu.
Now that netctl is removed, nothing requires dialog.

configs/releng/airootfs/etc/systemd/system/reflector.service:
Remove references to a nonexistent file.

The filesystem package installs /root as 750 not 700.

Move chmod from customize_airootfs.sh to build.sh.

Additionally update names of renamed packages:
https://git.archlinux.org/svntogit/packages.git/commit/trunk?h=packages/bind&id=1b097b9bcaddd65c7af4f92efef175f959395a7e
https://git.archlinux.org/svntogit/packages.git/commit/trunk?h=packages/vim&id=807b49bf022a6d523ca6215d5b34cd1e37457bd5

configs/releng/syslinux/archiso_tail.cfg:
APM is old and some motherboard firmwares have removed support for it.
reboot.c32 and poweroff.c32 will not work on such firmwares.
Add a help text to "Reboot" and "Power Off" boot menu entries that warns about requiring APM.

When built with CONFIG_FONT_TER16x32, the Linux kernel includes a TER16x32 font based on ter-i32b from terminus-font. The kernel will automatically choose this font on screen resolutions larger than 1920×1080.
The terminus-font package includes fonts for other character sets, which may be useful during installation.

Timeout is 3 seconds to match systemd-boot's configuration.

scripts/run_archiso.sh:
A script to run a built archiso image using qemu.
It can run the image on an emulated BIOS (using seabios) or UEFI (using edk2-ovmf) system.

.gitlab-ci.yml:
Adding scripts/run_archiso.sh to shellcheck call.

Closes #28

See https://wiki.archlinux.org/index.php/Kernel_mode_setting#Early_KMS_start .

It is enough if one network interface is online, there is no need to wait for all of them.
Without this, when connecting with Wi-Fi and leaving Ethernet disconnected, the network-online.target will get unnecessarily delayed.

archiso/mkarchiso:
Calls to _pacman() need to be done with multiple parameters (e.g. array) instead of one string, as string splitting is
not done in that function anymore.
Turning _iso_efi_boot_args from string into an array to have an easier time of passing it to xorriso.
Calling xorriso within the if statements instead of providing -quiet via variable.
Fixing command_install() to provide packages separately to _pacman()

configs/releng/build.sh:
Replacing all newlines when retrieving the packages from packages.x86_64 with spaces so they will be properly provided
to "mkarchiso install".

/etc/systemd/scripts/ is not a standard directory.

Run shellchek on the choose-mirror script.

Pacman's mirrolist will be updated by reflector.service in the live system.

reflector.service will update pacman's mirrorlist after a network connection is established in the live system.
Fixes #26 .

{configs/releng/efiboot/loader/entries/archiso-x86_64-{cd,usb}.conf,configs/releng/syslinux/archiso_{pxe,sys}.cfg}:
Standardizing the boot loader entry format by switching all entries to the form:
"Arch Linux install medium (<CARCH>[, <PROPERTY>])".
This removes the distinction between "CD" and "USB" when booting in UEFI "el-torito" (as the information is not useful).
Changing some of the syslinux help text as well to reflect this change. This also drops the specific <CARCH> from the
syslinux help text as it is duplicated information.

Closes #24

It was previously pulled in as a dependency of refind. Now that refind is removed, add efibootmgr explicitly.

It cannot be fully replaced by lsblk.

Reduce the time where boot loader artifacts linger on screen after the boot loader has done its job.

archiso/mkarchiso:
Quoting all variables.
Changing pkg_list to be an array instead of a string for easier
handling. Using read to properly populate pkg_list from OPTARG with
stripped whitespaces.
Not exporting iso_label anymore as there seems to be no reason to do so.
Introducing line breaks.

.editorconfig:
Setting max_line_length to 120.
Adding a section for YAML files (e.g. .gitlab-ci.yml).

configs/releng/build.sh
Quting nearly all variables.
Introducing line breaks.

configs/baseline/build.sh:
Quoting all variables.
Introducing line breaks.

.gitlab-ci.yml:
Adding gitlab CI for shelleck linting of the config build scripts, mkarchiso and startup scripts in releng.

Closes #19

configs/releng/airootfs/etc/systemd/network/20-{ethernet,wirless}.network:
Making sure that systemd-networkd enables DHCP capabilities also for
IPv6 ('DHCP=yes' and unsetting IPv6AcceptRA - see `man 5
systemd.network` for further information).

Closes #23

configs/releng/packages.x86_64:
Due to dropping netctl from the image, no packgae currently directly
pulls in a resolvconf provider.
The systemd-resolvconf package is compatible with systemd-resolved which
is in use on the image now and the preferred choice.

Closes #22

configs/releng/airootfs/etc/systemd/system/multi-user.target.wants/iwd.service:
Adding a symlink to /usr/lib/systemd/system/iwd.service to enable iwd in
airootfs (and thus on the image).

Closes #18

configs/releng/packages.x86_64:
Removing packages:
* grub :rescue/ installation actions for grub should be run from within
  a chroot
* lsscsi: lsblk provides the same functionality
* netctl: we have systemd-networkd enabled by default
* ntp: we have systemd-timesyncd
* refind: rescue/ installation actions for refind should be run from
  within a chroot
* vi: we have vim

Closes #15

configs/releng/build.sh:
Fixing wrong ownership of files when copying overlay modifications from
the config's airootfs directory to the working directory in
make_customize_airootfs() by using the cp flag
'--no-preserve=ownership'.

Thanks to Marcos Mello and Francois Dupoux of sysresccd
(https://gitlab.com/fdupoux/sysresccd-src) for making this fix
available.

Closes #11

configs/releng/packages.x86_64:
Adding nvme-cli to the list of packages for working with NVME drives in
a live environment (as discussed in FS#63769).

Closes #20

configs/releng/airootfs/root/.automated_script.sh:
Replacing wget with curl for the use-case of downloading a
pre-specified remote startup script (changing flags where needed).

configs/releng/packages.x86_64:
Removing wget from the list of installed packages, as
.automated_script.sh was the only reason for it being installed.

Closes #16

Adding a numerical prefix ('20-') to the ethernet.network and
wireless.network configuration files for systemd-networkd.
This way overriding them can become more predictable e.g. by providing
files with a '30-' prefix.

Closes #13