Buck: make target name same as git basename

Change-Id: I72737a4938720ce8d8c8892db225e081ed97e872
diff --git a/BUCK b/BUCK
index 8e99cda..271834c 100644
--- a/BUCK
+++ b/BUCK
@@ -1,5 +1,5 @@
 gerrit_plugin(
-  name = 'avatars-external',
+  name = 'external',
   srcs = glob(['src/main/java/**/*.java']),
   resources = glob(['src/main/resources/**/*']),
   manifest_entries = [