Fix the WebKit build.

A toolchain or other build change has added -Wnull-pointer-arithmetic
causing a build failure. This explicitly disables that warning.

WEB-8 #done

Change-Id: I401590340ea44d14ddda4aa8c4f5c519e9d5be4e
diff --git a/BUILD.gn b/BUILD.gn
index b1ecc06..a6a789b 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -76,17 +76,18 @@
     "-Wextra",
     "-Wformat-security",
     "-Wmissing-format-attribute",
-    "-Wno-format",
     "-Wno-expansion-to-defined",
+    "-Wno-format",
     "-Wno-max-unsigned-zero",
+    "-Wno-null-pointer-arithmetic",
     "-Wno-parentheses-equality",
+    "-Wno-pessimizing-move",
+    "-Wno-tautological-compare",
     "-Wno-unused-function",
     "-Wno-unused-label",
     "-Wno-unused-lambda-capture",
     "-Wno-unused-parameter",
     "-Wno-unused-variable",
-    "-Wno-pessimizing-move",
-    "-Wno-tautological-compare",
     "-Wpointer-arith",
     "-Wundef",
     "-Wwrite-strings",