Don't load assets unnecessarily when precompiling executables.

sdk/lib/_internal/pub/test/global/run/unknown_package_test.dart

Index: sdk/lib/_internal/pub/test/global/run/unknown_package_test.dart
diff --git a/sdk/lib/_internal/pub/test/global/run/unknown_package_test.dart b/sdk/lib/_internal/pub/test/global/run/unknown_package_test.dart
index e5a4bab07184a447763a5b0a93b311f84f84551a..291577a345b91bded1350f82f61c66588c324b24 100644
--- a/sdk/lib/_internal/pub/test/global/run/unknown_package_test.dart
+++ b/sdk/lib/_internal/pub/test/global/run/unknown_package_test.dart
@@ -10,7 +10,7 @@ import '../../test_pub.dart';
 main() {
   initConfig();
   integration('errors if the package is not activated', () {
-    servePackages([]);
+    serveNoPackages();
 
     schedulePub(args: ["global", "run", "foo:bar"],
         error: startsWith("No active package foo."),