Disable all warnings when compiling NSS.

runtime/tools/gyp/nss_configurations.gypi

 # Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 # This file is included to modify the configurations to build third-party
 # code from Mozilla's NSS and NSPR libraries, modified by the Chromium project.
 # This code is C code, not C++, and is not warning-free, so we need to remove
 # C++-specific flags, and add flags to supress the warnings in the code.
 # This file is included from gyp files in the runtime/bin/net directory.
 {
   'variables': {
     # Used by third_party/nss, which is from Chromium.
     # Include the built-in set of root certificate authorities.
     'exclude_nss_root_certs': 0,
     'os_posix%': 1,
     'os_bsd%': 0,
     'chromeos%': 0,
     'clang%': 0,
   },
   'target_defaults': {
     'cflags': [
-      '-Wno-unused-variable',
-      '-Wno-unused-but-set-variable',
-      '-Wno-missing-field-initializers',
-      '-Wno-uninitialized',
-      '-Wno-sign-compare',
-      '-Wno-empty-body',
-      '-Wno-type-limits',
-      '-Wno-pointer-to-int-cast',
+      '-w',
       '-UHAVE_CVAR_BUILT_ON_SEM',
     ],
     # Removes these flags from the list cflags.
     'cflags!': [
       # NSS code from upstream mozilla builds with warnings,
       # so we must allow warnings without failing.
       '-Werror',
       '-Wall',
       '-ansi',
       # Not supported for C, only for C++.
       '-Wnon-virtual-dtor',
       '-Wno-conversion-null',
       '-fno-rtti',
       '-fvisibility-inlines-hidden',
       '-Woverloaded-virtual',
     ],
     'configurations': {
       'Dart_Base': {
         'xcode_settings': {
+          'WARNING_CFLAGS': [
+            '-w',
+          ],
           'WARNING_CFLAGS!': [
             '-Wall',
             '-Wextra',
           ],
         },
       },
       # Dart_Debug and Dart_Release are merged after Dart_Base, so we can
       # override the 'ansi' and '-Werror' flags set at the global level in
       # tools/gyp/configurations_xcode.gypi.
       'Dart_Debug': {
         'xcode_settings': {
           # Remove 'ansi' setting.
           'GCC_C_LANGUAGE_STANDARD': 'c99',
           'GCC_TREAT_WARNINGS_AS_ERRORS': 'NO', # -Werror off
         },
       },
       'Dart_Release': {
         'xcode_settings': {
           # Remove 'ansi' setting.
           'GCC_C_LANGUAGE_STANDARD': 'c99',
           'GCC_TREAT_WARNINGS_AS_ERRORS': 'NO', # -Werror off
         },
       },
     },
   },
 }