ci: only run on nix tags

.gitlab-ci.yml

@@ -11,6 +11,8 @@ stages:
 # $UPDATE_FLAKE = flag to update the flake
 update:
   stage: flake
+  tags:
+    - nix
   # from https://forum.gitlab.com/t/git-push-from-inside-a-gitlab-runner/30554/5
   before_script:
     # set teh ssh key for the commit
@@ -39,6 +41,8 @@ update:
 
 build:
   stage: test
+  tags:
+    - nix
   before_script:
     - . "$HOME/.nix-profile/etc/profile.d/nix.sh"
     # use the new flake
@@ -56,6 +60,8 @@ build:
 # every commit on main will build and deploy
 deploy:
   stage: deploy
+  tags:
+    - nix
   before_script:
     # setup ssh key
     - eval $(ssh-agent -s)