Fix GN NaCl Debug build of base.

base/third_party/dynamic_annotations/BUILD.gn

 # Copyright (c) 2013 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.
 
 if (is_nacl) {
   # Native client doesn't need dynamic annotations, so we provide a
   # dummy target in order for clients to not have to special-case the
   # dependency.
-  group("dynamic_annotations") {
+  source_set("dynamic_annotations") {
+    sources = [
+      "dynamic_annotations.h",
+    ]
   }
 } else {
   source_set("dynamic_annotations") {
     sources = [
       "../valgrind/valgrind.h",
       "dynamic_annotations.c",
       "dynamic_annotations.h",
     ]
     if (is_android && !is_debug) {
       configs -= [ "//build/config/compiler:optimize" ]
       configs += [ "//build/config/compiler:optimize_max" ]
     }
   }
 }