ci: Allow lima jobs to be globally disabled

This is useful in situations like right now, where the boards are dead.

Signed-off-by: Daniel Stone <daniels@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16077>

.gitlab-ci.yml

@@ -20,6 +20,7 @@ variables:
   FD_FARM: "online"
   COLLABORA_FARM: "online"
   MICROSOFT_FARM: "offline"
+  LIMA_FARM: "offline"
 
 default:
   before_script:

.gitlab-ci/test-source-dep.yml

@@ -357,6 +357,8 @@
   stage: arm
   rules:
     - *ignore_scheduled_pipelines
+    - if: '$LIMA_FARM == "offline"'
+      when: never
     - changes:
         *mesa_core_file_list
       when: on_success