Explicitly reference framework-wifi app build rule

This works around a build-system limitation where it does not know
which jars to feed r8 to resolve all classes during proguarding.

Bug: 160453030
Bug: 169931783
Test: build_mainline_modules.sh (with prebuilt sdk)
Change-Id: I3d9f2049cf898b5e551a5c5764df423abaa5e92d
Merged-In: I3d9f2049cf898b5e551a5c5764df423abaa5e92d
diff --git a/Tethering/Android.bp b/Tethering/Android.bp
index 257538d..5526c65 100644
--- a/Tethering/Android.bp
+++ b/Tethering/Android.bp
@@ -101,6 +101,7 @@
     ],
     libs: [
         "framework-tethering",
+        "framework-wifi",
     ],
     jarjar_rules: "jarjar-rules.txt",
     optimize: {