Turn down warning level for GN build of image_diff utility

samples/BUILD.gn

 # Copyright 2014 PDFium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 group("samples") {
   deps = [
     ":pdfium_test",
     ":pdfium_diff",
   ]
 }
@@ skipping 26 matching lines @@
 executable("pdfium_diff") {
   sources = [
     "image_diff.cc",
     "image_diff_png.cc",
     "image_diff_png.h",
   ]
   deps = [
     "//third_party/pdfium",
     ":fx_lpng",
   ]
-  configs += [ ":pdfium_samples_config" ]
+  configs -= [ "//build/config/compiler:chromium_code" ]
+  configs += [
+    ":pdfium_samples_config",
+    "//build/config/compiler:no_chromium_code",
+  ]
 }
 
 static_library("fx_lpng") {
   sources = [
     "fx_lpng/include/fx_png.h",
     "fx_lpng/src/fx_png.c",
     "fx_lpng/src/fx_pngerror.c",
     "fx_lpng/src/fx_pngget.c",
     "fx_lpng/src/fx_pngmem.c",
     "fx_lpng/src/fx_pngpread.c",
     "fx_lpng/src/fx_pngread.c",
     "fx_lpng/src/fx_pngrio.c",
     "fx_lpng/src/fx_pngrtran.c",
     "fx_lpng/src/fx_pngrutil.c",
     "fx_lpng/src/fx_pngset.c",
     "fx_lpng/src/fx_pngtrans.c",
     "fx_lpng/src/fx_pngwio.c",
     "fx_lpng/src/fx_pngwrite.c",
     "fx_lpng/src/fx_pngwtran.c",
     "fx_lpng/src/fx_pngwutil.c",
   ]
   include_dirs = [
     "../core/src/fxcodec/fx_zlib/include/",
   ]
   configs += [ ":pdfium_samples_config" ]
 }