Use -fno-delete-null-pointer-checks with gcc builds

BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/android/config.gni")
 import("//build/config/arm.gni")
 import("//build/config/dcheck_always_on.gni")
 import("//build/config/mips.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 
@@ skipping 304 matching lines @@
     if (is_win) {
       # Increase the initial stack size. The default is 1MB, this is 2MB. This
       # applies only to executables and shared libraries produced by V8 since
       # ldflags are not pushed to dependants.
       ldflags += [ "/STACK:2097152" ]
     }
   }
   if (is_android && v8_android_log_stdout) {
     defines += [ "V8_ANDROID_LOG_STDOUT" ]
   }
+  if (!is_win && !is_clang) {
+    # GCC 6+ can optimize away pointer comparisons to null. This is
+    # problematic as V8 encodes Values through tagged pointers and comparisons
+    # with 0 are actually necessary in many cases. As a temporary Workaround
+    # we disable this optimization. See: https://crbug.com/v8/3782
+    cflags += [ "-fno-delete-null-pointer-checks" ]
+  }
 
   # TODO(jochen): Support v8_enable_prof on Windows.
   # TODO(jochen): Add support for compiling with simulators.
 
   if (is_debug) {
     if (is_linux && v8_enable_backtrace) {
       ldflags += [ "-rdynamic" ]
     }
 
     # TODO(jochen): Add support for different debug optimization levels.
@@ skipping 2274 matching lines @@
 
   deps = [
     ":fuzzer_support",
   ]
 
   configs = [ ":internal_config" ]
 }
 
 v8_fuzzer("wasm_code_fuzzer") {
 }