[gnome-build-meta/gnome-3-32] .gitlab-ci.yml: only run run the track job on branches targetting master

[Abderrahim Kitouni <akitouni src gnome org>]

commit aa5fcb62cbfbcb7c1bc09c1b91915a4f56526e13
Author: Abderrahim Kitouni <akitouni gnome org>
Date:   Fri Apr 19 16:11:09 2019 +0100

    .gitlab-ci.yml: only run run the track job on branches targetting master
    
    (cherry picked from commit 7790e2925d027299e37372719e9d41a393f777f2)

 .gitlab-ci.yml | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index f5a769f1..782d91b6 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -233,9 +233,10 @@ track:
   script:
     - ${BST} track --deps all core.bst flatpak-runtimes.bst
   retry: 2
-  # don't run on stable branches
-  except:
-    - /^gnome-\d-\d\d$/
+  # only run on branches targeting master
+  only:
+    variables:
+      - $FLATPAK_BRANCH == 'master'
   artifacts:
     when: always
     paths: