[infra] Assembles the SDK using GN rather than create_sdk.py

tools/gn.py

 #!/usr/bin/env python
 # Copyright 2016 The Dart project 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 argparse
 import multiprocessing
 import os
 import shutil
 import subprocess
 import sys
 import time
 import utils
 
 HOST_OS = utils.GuessOS()
 HOST_ARCH = utils.GuessArchitecture()
 SCRIPT_DIR = os.path.dirname(sys.argv[0])
 DART_ROOT = os.path.realpath(os.path.join(SCRIPT_DIR, '..'))
 GN = os.path.join(DART_ROOT, 'buildtools', 'gn')
 
 # Environment variables for default settings.
 DART_USE_ASAN = "DART_USE_ASAN"  # Use instead of --asan
 DART_USE_MSAN = "DART_USE_MSAN"  # Use instead of --msan
 DART_USE_TSAN = "DART_USE_TSAN"  # Use instead of --tsan
 DART_USE_WHEEZY = "DART_USE_WHEEZY"  # Use instread of --wheezy
 DART_USE_TOOLCHAIN = "DART_USE_TOOLCHAIN"  # Use instread of --toolchain-prefix
 DART_USE_SYSROOT = "DART_USE_SYSROOT"  # Use instead of --target-sysroot
+# use instead of --platform-sdk
+DART_MAKE_PLATFORM_SDK = "DART_MAKE_PLATFORM_SDK"
 
 def UseASAN():
   return DART_USE_ASAN in os.environ
 
 
 def UseMSAN():
   return DART_USE_MSAN in os.environ
 
 
 def UseTSAN():
   return DART_USE_TSAN in os.environ
 
 
 def UseWheezy():
   return DART_USE_WHEEZY in os.environ
 
 
 def ToolchainPrefix(args):
   if args.toolchain_prefix:
     return args.toolchain_prefix
   return os.environ.get(DART_USE_TOOLCHAIN)
 
 
 def TargetSysroot(args):
   if args.target_sysroot:
     return args.target_sysroot
   return os.environ.get(DART_USE_SYSROOT)
 
 
+def MakePlatformSDK():
+  return DART_MAKE_PLATFORM_SDK in os.environ
+
+
 def GetOutDir(mode, arch, target_os):
   return utils.GetBuildRoot(HOST_OS, mode, arch, target_os)
 
 
 def ToCommandLine(gn_args):
   def merge(key, value):
     if type(value) is bool:
       return '%s=%s' % (key, 'true' if value else 'false')
     return '%s="%s"' % (key, value)
   return [merge(x, y) for x, y in gn_args.iteritems()]
@@ skipping 123 matching lines @@
 
   dont_use_clang = DontUseClang(args, gn_args['target_os'],
                                       gn_args['host_cpu'],
                                       gn_args['target_cpu'])
   gn_args['is_clang'] = args.clang and not dont_use_clang
 
   gn_args['is_asan'] = args.asan and gn_args['is_clang']
   gn_args['is_msan'] = args.msan and gn_args['is_clang']
   gn_args['is_tsan'] = args.tsan and gn_args['is_clang']
 
+  gn_args['dart_platform_sdk'] = args.platform_sdk
+
   # Setup the user-defined sysroot.
   if gn_args['target_os'] == 'linux' and args.wheezy and not crossbuild:
     gn_args['dart_use_wheezy_sysroot'] = True
   else:
     sysroot = TargetSysroot(args)
     if sysroot:
       gn_args['target_sysroot'] = ParseStringMap(arch, sysroot)
 
     toolchain = ToolchainPrefix(args)
     if toolchain:
@@ skipping 140 matching lines @@
       default=os_has_ide(HOST_OS),
       action='store_true')
   other_group.add_argument('--msan',
       help='Build with MSAN',
       default=UseMSAN(),
       action='store_true')
   other_group.add_argument('--no-msan',
       help='Disable MSAN',
       dest='msan',
       action='store_false')
+  other_group.add_argument('--platform-sdk',
+      help='Directs the create_sdk target to create a smaller "Platform" SDK',
+      default=MakePlatformSDK(),
+      action='store_true')
   other_group.add_argument('--target-sysroot', '-s',
       type=str,
       help='Comma-separated list of arch=/path/to/sysroot mappings')
   other_group.add_argument('--toolchain-prefix', '-t',
       type=str,
       help='Comma-separated list of arch=/path/to/toolchain-prefix mappings')
   other_group.add_argument('--tsan',
       help='Build with TSAN',
       default=UseTSAN(),
       action='store_true')
@@ skipping 71 matching lines @@
       return 1
 
   endtime = time.time()
   if args.verbose:
     print ("GN Time: %.3f seconds" % (endtime - starttime))
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(Main(sys.argv))