Comment out not yet used flags from BUILD.gn

gn started to complain about unused variables

BUG=none
R=dcarney@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/292263003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21405 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

BUILD.gn

@@ -13,9 +13,9 @@ v8_enable_i18n_support = true
 v8_enable_verify_heap = false
 v8_interpreted_regexp = false
 v8_object_print = false
-v8_postmortem_support = false
+#v8_postmortem_support = false
 v8_use_default_platform = true
-v8_use_snapshot = true
+#v8_use_snapshot = true
 
 if (is_debug) {
   v8_enable_extra_checks = true