[simple-scan] Fix CI by installing GCC on Ubuntu

[Robert Ancell <rancell src gnome org>]

commit 542f9002e91ad323411bb8f4217a6648a0e38b6a
Author: Robert Ancell <robert ancell canonical com>
Date:   Fri Dec 8 10:57:40 2017 +1300

    Fix CI by installing GCC on Ubuntu

 .gitlab-ci.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index eb678e4..8c96847 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -6,7 +6,7 @@ build-ubuntu:
   stage: build
   before_script:
     - apt-get update
-    - apt-get install -q -y --no-install-recommends meson valac gettext itstool libgtk-3-dev libgusb-dev 
libcolord-dev libpackagekit-glib2-dev libwebp-dev libsane-dev
+    - apt-get install -q -y --no-install-recommends meson valac gcc gettext itstool libgtk-3-dev libgusb-dev 
libcolord-dev libpackagekit-glib2-dev libwebp-dev libsane-dev
   script:
     - meson _build
     - ninja -C _build install