[gobject-introspection] ci: Add missing package

[Emmanuele Bassi <ebassi src gnome org>]

commit 4c1f771104f9f637c4fc1d0e914c1c4e1c036709
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Thu Mar 29 12:06:43 2018 +0100

    ci: Add missing package
    
    We sadly need redhat-rpm-config because of Python's distutils.

 .gitlab-ci/Dockerfile | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/.gitlab-ci/Dockerfile b/.gitlab-ci/Dockerfile
index 01913f24..8691c0be 100644
--- a/.gitlab-ci/Dockerfile
+++ b/.gitlab-ci/Dockerfile
@@ -36,6 +36,7 @@ RUN dnf -y install \
     python3-mako \
     python3-pip \
     python3-wheel \
+    redhat-rpm-config \
     systemtap-sdt-devel \
     zlib-devel \
  && dnf clean all