Provide a label for the test suite

Although the plugin currently only has a single test, having a
separate label that matches the plugin's repository name allows easier
inclusion in CI systems.

Change-Id: I867de5dfa1c8473baea64c8c9d4e0365a2e9cbf9
diff --git a/BUCK b/BUCK
index b28f661..3aed93a 100644
--- a/BUCK
+++ b/BUCK
@@ -20,6 +20,7 @@
 java_test(
   name = 'cookbook_tests',
   srcs = glob(['src/test/java/**/*.java']),
+  labels = ['cookbook-plugin'],
   deps = [
     ':cookbook-plugin__plugin',
     '//lib:junit',