[gnome-system-monitor] Add libsystemd-dev as a system monitor dependency

[Robert Roth <robertroth src gnome org>]

commit 02e7e8228c50ac5e29086d8a093aaea6748ecf52
Author: ToMe25 <tome25 gmx de>
Date:   Sun Feb 27 18:56:19 2022 +0000

    Add libsystemd-dev as a system monitor dependency
    
    IDK why it wasn't one in the past

 .gitlab-ci.yml | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 4816bc36..219e82b1 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -31,7 +31,7 @@ variables:
     make
     texinfo
     texlive
-  UBUNTU_LIBHANDY_DEPENDENCIES:
+  UBUNTU_LIBHANDY_DEPENDENCIES: # packages required to build libhandy on ubuntu.
     libgladeui-2-6
     valac
   UBUNTU_DEPENDENCIES: # packages required to build the system monitor on ubuntu.
@@ -39,8 +39,9 @@ variables:
     git
     itstool
     libglibmm-2.4-dev
-    librsvg2-dev
     libgtkmm-3.0-dev
+    librsvg2-dev
+    libsystemd-dev
     libxml2-dev
     meson