[infra] Begin removing gyp

tools/generate_buildfiles.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 os
 import subprocess
 import sys
 import utils
 
 HOST_OS = utils.GuessOS()
 SCRIPT_DIR = os.path.dirname(sys.argv[0])
 DART_ROOT = os.path.realpath(os.path.join(SCRIPT_DIR, '..'))
-DART_USE_GYP = "DART_USE_GYP"
 DART_DISABLE_BUILDFILES = "DART_DISABLE_BUILDFILES"
 
 
-def UseGyp():
-  return DART_USE_GYP in os.environ
-
-
 def DisableBuildfiles():
   return DART_DISABLE_BUILDFILES in os.environ
 
 
 def Execute(args):
   process = subprocess.Popen(args, cwd=DART_ROOT)
   process.wait()
   return process.returncode
 
 
@@ skipping 44 matching lines @@
 def RunGn(options):
   status = RunHostGn(options)
   if status != 0:
     return status
   status = RunCrossGn(options)
   if status != 0:
     return status
   return RunAndroidGn(options)
 
 
-def RunGyp(options):
-  gyp_command = [
-    'python',
-    os.path.join(DART_ROOT, 'tools', 'gyp_dart.py'),
-  ]
-  if options.verbose:
-    print ' '.join(gyp_command)
-  return Execute(gyp_command)
-
-
 def ParseArgs(args):
   args = args[1:]
   parser = argparse.ArgumentParser(
       description="A script to generate Dart's build files.")
 
   parser.add_argument("-v", "--verbose",
       help='Verbose output.',
       default=False,
       action="store_true")
-  parser.add_argument("--gn",
-      help='Use GN',
-      default=not UseGyp(),
-      action='store_true')
-  parser.add_argument("--gyp",
-      help='Use gyp',
-      default=UseGyp(),
-      action='store_true')
 
-  options = parser.parse_args(args)
-  # If gyp is enabled one way or another, then disable gn
-  if options.gyp:
-    options.gn = False
-  return options
+  return parser.parse_args(args)
 
 
 def main(argv):
   # Check the environment and become a no-op if directed.
   if DisableBuildfiles():
     return 0
   options = ParseArgs(argv)
-  if options.gn:
-    return RunGn(options)
-  else:
-    return RunGyp(options)
+  RunGn(options)
 
 
 if __name__ == '__main__':
     sys.exit(main(sys.argv))