Add wifi-module-sdk build target.

Bug: 177884752
Test: m wifi-module-sdk
Change-Id: I22c9f2d7a8a5f9b84f66012be91ec32a8232f30d
diff --git a/apex/Android.bp b/apex/Android.bp
index b3597c1..156817b 100644
--- a/apex/Android.bp
+++ b/apex/Android.bp
@@ -63,3 +63,10 @@
     name: "com.android.wifi.certificate",
     certificate: "com.android.wifi",
 }
+
+sdk {
+    name: "wifi-module-sdk",
+    java_sdk_libs: [
+        "framework-wifi",
+    ],
+}