Explain why attempts to remove the libc++ dependency are futile.

This isn't as useless as it seems though. It should prevent me from
going down this path a third time, and it removes one pointless barrier
that gets in the way of running a toybox binary on an older release.

Change-Id: Ia193eb7af162878a331db1b1e1c90ff0f617becb
diff --git a/Android.mk b/Android.mk
index 3186eda..068eb8c 100644
--- a/Android.mk
+++ b/Android.mk
@@ -213,6 +213,10 @@
 
 LOCAL_SHARED_LIBRARIES := libcutils libselinux
 
+# This doesn't actually prevent us from dragging in libc++ at runtime
+# because libnetd_client.so is C++.
+LOCAL_CXX_STL := none
+
 LOCAL_MODULE := toybox
 
 # dupes: dd df du ls renice