[gn] Move build to gypfiles

build/set_clang_warning_flags.gypi

-# Copyright 2016 the V8 project authors. All rights reserved.
-# Copyright (c) 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.
-
-# This file is meant to be included to set clang-specific compiler flags.
-# To use this the following variable can be defined:
-#   clang_warning_flags:       list: Compiler flags to pass to clang.
-#   clang_warning_flags_unset: list: Compiler flags to not pass to clang.
-#
-# Only use this in third-party code. In chromium_code, fix your code to not
-# warn instead!
-#
-# Note that the gypi file is included in target_defaults, so it does not need
-# to be explicitly included.
-#
-# Warning flags set by this will be used on all platforms. If you want to set
-# warning flags on only some platforms, you have to do so manually.
-#
-# To use this, create a gyp target with the following form:
-# {
-#   'target_name': 'my_target',
-#   'variables': {
-#     'clang_warning_flags': ['-Wno-awesome-warning'],
-#     'clang_warning_flags_unset': ['-Wpreviously-set-flag'],
-#   }
-# }
-
-{
-  'variables': {
-    'clang_warning_flags_unset%': [],  # Provide a default value.
-  },
-  'conditions': [
-    ['clang==1', {
-      # This uses >@ instead of @< to also see clang_warning_flags set in
-      # targets directly, not just the clang_warning_flags in target_defaults.
-      'cflags': [ '>@(clang_warning_flags)' ],
-      'cflags!': [ '>@(clang_warning_flags_unset)' ],
-      'xcode_settings': {
-        'WARNING_CFLAGS': ['>@(clang_warning_flags)'],
-        'WARNING_CFLAGS!': ['>@(clang_warning_flags_unset)'],
-      },
-      'msvs_settings': {
-        'VCCLCompilerTool': {
-          'AdditionalOptions': [ '>@(clang_warning_flags)' ],
-          'AdditionalOptions!': [ '>@(clang_warning_flags_unset)' ],
-        },
-      },
-    }],
-    ['clang==0 and host_clang==1', {
-      'target_conditions': [
-        ['_toolset=="host"', {
-          'cflags': [ '>@(clang_warning_flags)' ],
-          'cflags!': [ '>@(clang_warning_flags_unset)' ],
-        }],
-      ],
-    }],
-  ],
-}