Write a phony target for the top-level directory of a create_bundle target.

tools/gn/bundle_data.cc

Index: tools/gn/bundle_data.cc
diff --git a/tools/gn/bundle_data.cc b/tools/gn/bundle_data.cc
index 7faccbdc51a6442ddec6626e31af77f53d38f03c..f1b60c0084839e5708b37ba4337c80b84496c16e 100644
--- a/tools/gn/bundle_data.cc
+++ b/tools/gn/bundle_data.cc
@@ -5,6 +5,7 @@
 #include "tools/gn/bundle_data.h"
 
 #include "base/logging.h"
+#include "tools/gn/filesystem_utils.h"
 #include "tools/gn/output_file.h"
 #include "tools/gn/settings.h"
 #include "tools/gn/target.h"
@@ -103,6 +104,9 @@ void BundleData::GetOutputsAsSourceFiles(
 
   if (!asset_catalog_sources_.empty())
     outputs_as_source->push_back(GetCompiledAssetCatalogPath());
+
+  if (!root_dir_.empty())
+    outputs_as_source->push_back(GetBundleRootDirOutput(settings));
 }
 
 SourceFile BundleData::GetCompiledAssetCatalogPath() const {
@@ -110,3 +114,18 @@ SourceFile BundleData::GetCompiledAssetCatalogPath() const {
   std::string assets_car_path = resources_dir_ + "/Assets.car";
   return SourceFile(SourceFile::SWAP_IN, &assets_car_path);
 }
+
+SourceFile BundleData::GetBundleRootDirOutput(const Settings* settings) const {
+  const SourceDir& build_dir = settings->build_settings()->build_dir();
+  std::string bundle_root_relative = RebasePath(root_dir(), build_dir);
+
+  size_t first_component = bundle_root_relative.find('/');
+  if (first_component != std::string::npos) {
+    base::StringPiece outermost_bundle_dir =
+        base::StringPiece(bundle_root_relative).substr(0, first_component);
+    std::string return_value(build_dir.value());
+    outermost_bundle_dir.AppendToString(&return_value);
+    return SourceFile(SourceFile::SWAP_IN, &return_value);
+  }
+  return SourceFile(root_dir());
+}