ci: add gitlab ci

Signed-off-by: Filipe Laíns <lains@archlinux.org>
Signed-off-by: Lukas Fleischer <lfleischer@archlinux.org>

.gitlab-ci.yml

+image: archlinux
+
+before_script:
+  - pacman -Syu --noconfirm --noprogressbar --needed
+           base-devel git gpgme protobuf pyalpm python-mysql-connector
+           python-pygit2 python-srcinfo python-bleach python-markdown
+           python-sqlalchemy python-alembic python-pytest python-werkzeug
+           python-pytest-tap
+
+test:
+  script:
+    - make -C test