Generates includes for imported flatbuffers schemas.

Because includes are generated without directory, this exports the
directory where generated headers are produced to the include path of
the dependent target.

Change-Id: I8058553f69aadf29cc1a2926fc27664d023e6e1d
diff --git a/flatbuffer.gni b/flatbuffer.gni
index d4164a5..96cd180 100644
--- a/flatbuffer.gni
+++ b/flatbuffer.gni
@@ -53,7 +53,9 @@
   set_sources_assignment_filter([])
 
   action_name = "${target_name}_gen"
+  config_name = "${target_name}_config"
   source_set_name = target_name
+
   compiled_action_foreach(action_name) {
     visibility = [ ":$source_set_name" ]
 
@@ -74,7 +76,6 @@
     args = [
       "-I",
       rebase_path("//"),
-      "--no-includes",
       "-c",
       "-o",
       "$out_dir",
@@ -87,6 +88,10 @@
     }
   }
 
+  config(config_name) {
+    include_dirs = get_path_info(get_target_outputs(":$action_name"), "dir")
+  }
+
   source_set(target_name) {
     forward_variables_from(invoker,
                            [
@@ -104,7 +109,10 @@
       testonly = invoker.testonly
     }
 
-    public_configs = [ "//third_party/flatbuffers:flatbuffers_config" ]
+    public_configs = [
+      "//third_party/flatbuffers:flatbuffers_config",
+      ":$config_name",
+    ]
 
     public_deps = [
       # The generated headers reference headers within flatbuffers, so