Reland Automatically download gold plugin for cfi builds.

DEPS

Index: DEPS
diff --git a/DEPS b/DEPS
index 0c6cda6077c0d75680bd948bd9cc3ca1dea74742..c06da810796e4c0752daa9bdc4b1722ff26be7ed 100644
--- a/DEPS
+++ b/DEPS
@@ -103,6 +103,13 @@ hooks = [
     ],
   },
   {
+    # Pull gold plugin if needed or requested via GYP_DEFINES.
+    # Note: This must run before the clang update.
+    'name': 'gold_plugin',
+    'pattern': '.',
+    'action': ['python', 'v8/build/download_gold_plugin.py'],
+  },
+  {
     # Pull clang if needed or requested via GYP_DEFINES.
     # Note: On Win, this should run after win_toolchain, as it may use it.
     'name': 'clang',