Older versions of doas do not support /etc/doas.d/ yet, so after
downgrading alpinelinux, buildozer does is not allowed to use doas
anymore.

Add a symlink from /etc/doas.conf to /etc/doas.d/doas.conf so that it
keeps working.

See merge request !3

sudo has been moved to community, and we want to switch from doas to
sudo in this image.

A symlink from sudo to doas is still provided to make sure the
alpine-gitlab-ci image does not break.

See #1

abuild no longer depends on sudo, so we need to make sure to install it.

This is a dependency required to build gcc with ada support, but cannot
be added as a makedepends because that would create a circular
dependency.

So pre-install it so that it's available already.

sudo does not like it when it's world readable.

Sudo started to emit the warning:

> setrlimit(RLIMIT_CORE): Operation not permitted

This is a [known issue][redhat-bug], and there is a workaround, so lets
add that workaround to reduce the noise.

[redhat-bug]: https://bugzilla.redhat.com/show_bug.cgi?id=1773148