Allow vendor code to link to libandroid_net.

This library contains only the multinetwork API, which is part
of the NDK and has long-term support. It is needed by any native
that wants to use network communications on a different network
than the default network, and thus is necessary for vendor code
such as IMS clients or carrier applications.

Bug: 37527489
Test: marlin builds and boots
Test: MultinetworkApiTest CTS tests passes
Change-Id: I2aa592d1d082aae410173adf2a09f6d1dd8092dc
diff --git a/native/android/libandroid_net.map.txt b/native/android/libandroid_net.map.txt
new file mode 100644
index 0000000..9b5a5a1
--- /dev/null
+++ b/native/android/libandroid_net.map.txt
@@ -0,0 +1,10 @@
+# These functions have been part of the NDK since API 24.
+# They are also all available to vendor code.
+LIBANDROID_NET {
+  global:
+    android_setsocknetwork; # vndk
+    android_setprocnetwork; # vndk
+    android_getaddrinfofornetwork; # vndk
+  local:
+    *;
+};