add macos 11 tests

.buildkite/ci.yml

@@ -123,6 +123,21 @@ steps:
         command:
           - "./scripts/runner.node.mjs darwin-aarch64-build-bun"
 
+      - key: "darwin-aarch64-test-macos-11"
+        label: ":darwin: 11 aarch64 - bun-test"
+        parallelism: 1
+        soft_fail:
+          - exit_status: 2
+        depends_on:
+          - "darwin-aarch64-build-bun"
+        agents:
+          queue: "test-darwin"
+          os: "darwin"
+          arch: "aarch64"
+          release: "11"
+        command:
+          - "./scripts/runner.node.mjs darwin-aarch64-build-bun"
+
   # macOS x64
   - key: "darwin-x64"
     group: ":darwin: x64"