ci: use Nix Buildkite plugin v2.2.0

Signed-off-by: Drew Hess <[email protected]>

Author: dhess

.buildkite/pipeline.yaml

@@ -10,13 +10,13 @@ steps:
   - command: nix-buildkite
     label: ":nixos: :buildkite:"
     plugins:
-      - hackworthltd/nix#v2.1.0:
+      - hackworthltd/nix#v2.2.0:
           expr: ".#hydraJobs"
           use-nix-build: "true"
           attr-prefix: ".#hydraJobs."
-          nix-build-opts: --max-jobs 0 --print-build-logs --eval-store auto --store 'ssh-ng://[email protected]?ssh-key=/etc/secrets/remote-builder-ssh-key'
-          nix-eval-jobs-args: --workers 8 --max-memory-size 8GiB --flake --force-recurse
+          nix-eval-jobs-args: --workers 4 --max-memory-size 8GiB --flake --force-recurse
           agent-tags: queue=nix-build,os=linux
+          darwin-step-agent-tags: os=darwin
 
   - wait