Move compilation of libicing.so into appsearch:appsearch.

We haven't been able to get an externally built libicing.so properly
included into appsearch-release.aar any other way yet (b/161205849).

Since nothing in external/icing is being uploaded to maven or
snapshotted into g3, the native lib is not available to dogfood.

Bug: 161205849
Test: Manual inspection of appsearch-release.aar
Change-Id: I76ac2beb59b2ed7f3e0a2e8710df690e366102c0
diff --git a/build.gradle b/build.gradle
index d6aea25..3901078 100644
--- a/build.gradle
+++ b/build.gradle
@@ -50,14 +50,15 @@
             manifest.srcFile 'AndroidManifest.xml'
             proto.srcDir 'proto/'
         }
-        androidTest.java.srcDir 'java/tests/instrumentation/'
+        // TODO(b/161205849): Re-enable this test once icing nativeLib is no longer being built
+        //  inside appsearch:appsearch.
+        //androidTest.java.srcDir 'java/tests/instrumentation/'
     }
 }
 
 dependencies {
     api('androidx.annotation:annotation:1.1.0')
 
-    implementation project(':icing:nativeLib')
     implementation('com.google.protobuf:protobuf-javalite:3.10.0')
 
     androidTestImplementation(ANDROIDX_TEST_CORE)