Add link to change that implements standalone build

Change-Id: Id886e0dbeeb87823a0a5c6412df7a70f91c2a33f

BUCK

diff --git a/BUCK b/BUCK
index 1bbb56a..ce101a9 100644
--- a/BUCK
+++ b/BUCK
@@ -1,3 +1,14 @@
+# This plugin currently does not support a standalone build, as a
+# standalone build was deemed too much maintenance overhead in its
+# present (2015-09-20) form.
+#
+# Once the standalone build does no longer come with a maintenance
+# overhead, a first shot at the standalone build for this plugin can
+# be found at:
+#
+#   https://gerrit-review.googlesource.com/#/c/70896/
+#
+
 include_defs('//bucklets/gerrit_plugin.bucklet')
 
 DEPS = [