[simple-scan] Enabling Arch Linux in the CI pipeline

[Robert Ancell <rancell src gnome org>]

commit 99aa68882fd3ad417469fbd06f18dd25d8b7216f
Author: Ox0000 <Ox0000 epistulae net>
Date:   Fri Sep 13 08:59:33 2019 -0400

    Enabling Arch Linux in the CI pipeline

 .gitlab-ci.yml | 8 ++++++++
 1 file changed, 8 insertions(+)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 92d8b82..3f07b94 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -14,3 +14,11 @@ build-fedora:
   script:
     - meson _build
     - ninja -C _build install
+
+build-arch:
+  image: archlinux/base:latest
+  before_script:
+    - pacman -Syu --noconfirm meson vala gettext itstool gtk3 libgusb colord libwebp sane
+  script:
+    - meson _build
+    - ninja -C _build install