Fix GN toolchains to use proper out dir.

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index 1b81c35c878567bd5d3bf55651ea1782022caf5f..6ed045c2ec436be10205fa5d9f436d4d5c71f641 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -10,17 +10,6 @@
 
 import("//build/config/ui.gni")
 
-# Android GN build has some bugs: http://crbug.com/405686
-if (is_android) {
-
-group("root") {
-  deps = [
-    "//base",
-  ]
-}
-
-} else {
-
 # In GN, a "group" is a dummy target that just lists other targets.
 group("root") {
   # Note that some dependencies are commented out. These are things that are
@@ -248,5 +237,3 @@ group("root") {
     ]
   }
 }
-
-}