Disable clang unsafe pointer arithmentics warning

Change-Id: Ia1b12f0ea058e4b29b16e99dd26565ce15bdf392
diff --git a/gn/standalone/BUILD.gn b/gn/standalone/BUILD.gn
index bd21589..329aa97 100644
--- a/gn/standalone/BUILD.gn
+++ b/gn/standalone/BUILD.gn
@@ -84,6 +84,7 @@
       "-Wno-reserved-identifier",
       "-Wno-unknown-sanitizers",
       "-Wno-unknown-warning-option",
+      "-Wno-unsafe-buffer-usage",
     ]
   } else if (!is_clang && !is_win) {
     # Use return std::move(...) for compatibility with old GCC compilers.