These build errors are caused because eglplatform.h is included before Qt
headers and it pulls X11 headers which contain many problematic macros.
Apparently X11 headers aren't required here anyways so let's just disable
them from being pulled in.
The regular zstd package has switched so the static-compat needs to switch
as well as otherwise the CMake find module from the regular package is
picked up (e.g. by Qt 6).
* Add my GPG key to the pacman keyring (not nice to hard-code it in the
Dockerfile but good enough for now)
* Install ccache into the base image to support makepkg's ccache option
* Split syncing packages and execution of `makepkg` so syncing can be
avoided when only building source package
* Don't quote `CRE`, it is unlikely spaces are needed here and using
chained commands (e.g. `sudo …`) might be useful
* Add documentation
* Allow building Arch Linux packages within a "standard" container similar
to how `makechrootpkg` allows building packages within a systemd-nspawn
container
* Add a Dockerfile to create an Arch Linux image suitable for package
builds via `makepkg`
It wouldn't be possible to keep it nevertheless because then
we needed to add gcc-d to make dependencies which is not possible
because the regular package dropped it. It is also not possible
to build with the previous version of static-compat-gcc because
it would fail to find gmp and some other libs (using them from
the host system would be technically possible but one needed to
workaround linker errors with the C runtime).
For some reason also libobjc is missing but I suppose that's not
a bit loss.
We must not link statically against it because it is also pulled by the
shared GLX library and would therefore end up multiple times in the apps
address space causing crashes. It should be stable enough anyways to not
having to bundle it. Since 1.6.x is still the newest version on older
distributions we must downgrade the version, though.
