More work cleaning up the BUILD files

Change-Id: I47fb18e7a12cd7e081631a5369274ef1e25f22c4
diff --git a/aos/BUILD b/aos/BUILD
new file mode 100644
index 0000000..97a033f
--- /dev/null
+++ b/aos/BUILD
@@ -0,0 +1,6 @@
+filegroup(
+  name = 'prime_binaries',
+  visibility = ['//visibility:public'],
+  srcs = [
+  ],
+)