Android: allow libnos to link with different datagram implementations

This removes the hard linking to the Citadel implementation.

Change-Id: I1a3ee719ad73351294744fbdeb0373bf4590903c
diff --git a/Android.bp b/Android.bp
index 2f59f5d..29289da 100644
--- a/Android.bp
+++ b/Android.bp
@@ -37,10 +37,8 @@
         "-Wno-extended-offsetof",
         "-Wno-unused-parameter",
     ],
-    header_libs: [
-        "nos_headers",
-        "libnos_headers",
-    ],
+    header_libs: ["nos_headers"],
+    shared_libs: ["libnos"]
 }
 
 cc_defaults {