move bpf test map into a separate file

This allows for better separation of test vs production code:
we will add more test maps and programs here later.

Test: builds
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I7b22e3e148ebf43fdf43dc68d0dea354f7627688
diff --git a/Tethering/apex/Android.bp b/Tethering/apex/Android.bp
index c99121c..7970944 100644
--- a/Tethering/apex/Android.bp
+++ b/Tethering/apex/Android.bp
@@ -27,7 +27,10 @@
     jni_libs: [
         "libservice-connectivity",
     ],
-    bpfs: ["offload.o"],
+    bpfs: [
+        "offload.o",
+        "test.o",
+    ],
     apps: ["Tethering"],
     manifest: "manifest.json",
     key: "com.android.tethering.key",