Create the directory for the plugin package

pkg/analyzer_plugin/BUILD.gn

+# Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+# for details. All rights reserved. Use of this source code is governed by a
+# BSD-style license that can be found in the LICENSE file.
+
+import("//build/dart/dart_package.gni")
+
+dart_package("analyzer_plugin") {
+  package_name = "analyzer_plugin"
+
+  source_dir = "lib"
+
+  deps = [
+    "//dart/pkg/analyzer",
+    "//dart/pkg/front_end",
+    "//third_party/dart-pkg/pub/args",
+    "//third_party/dart-pkg/pub/charcode",
+    "//third_party/dart-pkg/pub/crypto",
+    "//third_party/dart-pkg/pub/glob",
+    "//third_party/dart-pkg/pub/html",
+    "//third_party/dart-pkg/pub/isolate",
+    "//third_party/dart-pkg/pub/meta",
+    "//third_party/dart-pkg/pub/package_config",
+    "//third_party/dart-pkg/pub/path",
+    "//third_party/dart-pkg/pub/plugin",
+    "//third_party/dart-pkg/pub/watcher",
+    "//third_party/dart-pkg/pub/yaml",
+  ]
+}