Separate out target defaults in the GN build config.

testing/test.gni

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # ==============================================================================
 # TEST SETUP
 # ==============================================================================
 
 template("_gen_isolate") {
   testonly = true
@@ skipping 344 matching lines @@
     if (defined(invoker.output_name) && target_name != invoker.output_name) {
       group("${invoker.output_name}_run") {
         testonly = true
         deps = [
           ":${invoker.target_name}",
         ]
       }
     }
   }
 }
+
+# Test defaults.
+set_defaults("test") {
+  if (is_android) {
+    configs = default_shared_library_configs
+  } else {
+    configs = default_executable_configs
+  }
+}