CI: use large runner for autoupdate (MR 5498)

Since we build linux-next before pushing to BPO, use the big runner so
we don't delay the update by hours. BPO needs to build it *again* too...

would be nice if we could push the artifact directly, ah well.

Signed-off-by: Caleb Connolly <caleb@postmarketos.org>

.gitlab-ci.yml

@@ -174,6 +174,9 @@ build-riscv64:
 
 auto-update:
   stage: autoupdate
+  # We build packages before merging too
+  tags:
+    - saas-linux-large-amd64
   rules:
     # This variable is set in the scheduled pipeline configuration. It should be a space separated list of
     # package names to update.