[gtk] ci: Restore ccache, but do not cache it across jobs

[Emmanuele Bassi <ebassi src gnome org>]

commit 0b4e0ce50937694763aead07ac1d03a5e18c6ac8
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Thu Mar 15 12:01:45 2018 +0000

    ci: Restore ccache, but do not cache it across jobs
    
    The GitLab cache is kept across jobs, whether they succeeded or not:
    this means that if a compiler check fails during the Meson
    configuration, the small compiler program gets cached and restored the
    next time the job is run, thus failing again.

 .gitlab-ci.yml        | 1 -
 .gitlab-ci/Dockerfile | 1 +
 2 files changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 9bae24e751..33d2276de0 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -10,7 +10,6 @@ before_script:
 
 cache:
   paths:
-    - _ccache/
     - subprojects/gdk-pixbuf/
     - subprojects/glib/
     - subprojects/graphene/
diff --git a/.gitlab-ci/Dockerfile b/.gitlab-ci/Dockerfile
index c940ef6eaf..2413b81f53 100644
--- a/.gitlab-ci/Dockerfile
+++ b/.gitlab-ci/Dockerfile
@@ -7,6 +7,7 @@ RUN dnf -y install \
     avahi-gobject-devel \
     cairo-devel \
     cairo-gobject-devel \
+    ccache \
     colord-devel \
     cups-devel \
     desktop-file-utils \