Allow for locks to be inherited.  Inheriting the lock is something that
mkarchroot could do previously, but has since lost the ability to do.  This
allows for the programs to be more compos-able.

Do this by instead of unconditionally opening $file on $fd, first check if
$file is already open on $fd; and go ahead use it if it is.

The naive way of doing this would be to `$(readlink /dev/fd/$fd)` and
compare that to `$file`.  However, if `$file` is itself a symlink; or there
is a symlink somewhere in the path to `$file`, then this could easily fail.
Instead, check `[[ "/dev/fd/$fd" -ef "$file" ]]`.  Even though the Bash
documentation (`help test`) says that `-ef` checks for if the two files are
hard links to eachother, because it uses stat(3) (which resolves symlinks)
to do this check, it also works with the /dev/fd/ soft links.

`lock_close FD` is easier to remember than 'exec FD>&-`; and is especially
easier if FD is a variable (though that isn't actually taken advantage of
here).

This uses Bash 4.1+ `exec {var}>&-`, rather than the clunkier
`eval exec "$var>&-"` that was necessary in older versions of Bash.
Thanks to Dave Reisner for pointing this new bit of syntax out to me
the last time I submitted this (back in 2014, 4.1 had just come out).

The systemd package creates a subvolume at /var/lib/machines (through
tmpfiles), if it can. We need to delete this subvolume before we can
delete the parent subvolume.

Look through the root for inodes with the number 256. These identify
subvolume roots.

Move the function and save the orig_argv right along it.

makepkg --asroot was removed with pacman 4.2. Allow to specify a
separate makepkg user from the command line instead.

Fixes FS#43432

The way in which makechrootpkg reads variables from makepkg.conf(5) is
different from makepkg, in that it reads a subset of defined
variables, and only if the were not set in the environment before.

Mention this in the usage text.

Fixes FS#44827

This removes the preservation of HOME being /build just for the pacman
sudo call. Former leads to unbuildable packages when an to be installed
dependency writes something into the HOME dir (f.e. .config). The
resulting directories won't be writable by the builduser as they are
owned by root:root and ultimately will fail to build anything that
requires so.

In order to have an UTF-8 locale in the build root. This is something
normally set on real machines but is not set from our chroots. Meson,
for example, loudly complains when the locale charset is not UTF-8.

I'd like to have C.UTF-8, as most other distributions do. Unfortunately,
it's not part of vanilla glibc; en_US.UTF-8 will have to do.

mkarchroot already creates roots with both en_US.UTF-8 and de_DE.UTF-8,
the latter because builds of gcc (perhaps used to) require it.

Bump the CHROOT_VERSION due to the setting change.

The gnustep-base package ships a profile.d script that adds
"$HOME/GNUstep/Tools" to the PATH, which breaks when the user changes
and causes meson to exit with a "permission denied" error.

Make use of load_vars returning 1 when the file is missing. Avoids
introducing another variable.

Implemented the same way as in makepkg.

Signed-off-by: Johannes Löthberg <johannes@kyriasis.com>

Avoids having to specify them in dependency order.

Copy both UID and primary GID of the invoker to the builduser. Mount
srcdest and startdir read-write.

v2: Fixed GnuPG keyring owner and moved running namcap from a heredoc
    to a function.

This makes it a lot easier to swap out the host that actually serves the repos in the future.

Having it set to nologin breaks a couple of tests in Git and Python.

This way the HOME dir is writable and no ugly hacks are required
in the PKGBUILD if $HOME is accessed (f.e. maven, gradle and also
some python tests etc.)

It is passed down to the container when stdin/stdout is not a tty; this
is the case when archbuild's output is redirected to a pipe or file.

This is needed in order to use GPG's auto-key-retrieve keyserver option,
otherwise the keyring will get copied to the chroot before the required
keys are retrieved during 'makepkg --verifysource'.