[calls] ci: Use PKG_ONLY variable to exclude flatpak job

[Evangelos Ribeiro Tzaras <devrtz src gnome org>]

commit fe7ebf51ce997d1911b1027152ca4bd6c2f961ba
Author: Evangelos Ribeiro Tzaras <devrtz fortysixandtwo eu>
Date:   Mon Nov 29 10:30:32 2021 +0100

    ci: Use PKG_ONLY variable to exclude flatpak job
    
    This makes sure we're not wasting computational resources when we only
    want to build debian packages.

 .gitlab-ci.yml | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index e5e58a2a..27053268 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -119,6 +119,9 @@ package-deb-pureos-byzantium:arm64:
       paths:
         - '.flatpak-builder/cache'
         - '.flatpak-builder/ccache'
+  except:
+    variables:
+      - $PKG_ONLY == "1"
 
 flatpak:master:
   extends: .flatpak