More work cleaning up the BUILD files

Change-Id: I47fb18e7a12cd7e081631a5369274ef1e25f22c4
diff --git a/aos/testing/BUILD b/aos/testing/BUILD
new file mode 100644
index 0000000..2365bd8
--- /dev/null
+++ b/aos/testing/BUILD
@@ -0,0 +1,10 @@
+cc_library(
+  name = 'googletest',
+  visibility = ['//visibility:public'],
+  srcs = [
+    'gtest_main.cc',
+  ],
+  deps = [
+    '//third_party/googletest',
+  ],
+)