Add a hidden --no-package-symlinks flag.

sdk/lib/_internal/pub/bin/pub.dart

Index: sdk/lib/_internal/pub/bin/pub.dart
diff --git a/sdk/lib/_internal/pub/bin/pub.dart b/sdk/lib/_internal/pub/bin/pub.dart
index ab95fc6ecf0ccf45d3a42eb5ff68f67d6f32f997..35b8c90ef63e1d6a326d49c14ea34cd61e71c93b 100644
--- a/sdk/lib/_internal/pub/bin/pub.dart
+++ b/sdk/lib/_internal/pub/bin/pub.dart
@@ -173,7 +173,7 @@ Future invokeCommand(String cacheDir, ArgResults mainOptions) {
   }
 
   return syncFuture(() {
-    return command.run(cacheDir, options);
+    return command.run(cacheDir, mainOptions, options);
   }).whenComplete(() {
     command.cache.deleteTempDir();
   });