add protobuf configuration
diff --git a/buildkite/pipelines/protobuf-postsubmit.json b/buildkite/pipelines/protobuf-postsubmit.json
new file mode 100644
index 0000000..225fe51
--- /dev/null
+++ b/buildkite/pipelines/protobuf-postsubmit.json
@@ -0,0 +1,8 @@
+{
+  "platforms": {
+    "ubuntu1404": {"test_targets": ["//:all"]},
+    "ubuntu1604": {"test_targets": ["//:all"]},
+    "macos": {"test_targets": ["//:all"]}
+  }
+}
+