[infra] Translate _sources.gypi files to _sources.gni files

tools/ninja.py

 #!/usr/bin/env python
 #
 # Copyright (c) 2017, 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.
 
 import multiprocessing
 import optparse
 import os
 import subprocess
 import sys
 import time
 import utils
 
 HOST_OS = utils.GuessOS()
 HOST_CPUS = utils.GuessCpus()
 SCRIPT_DIR = os.path.dirname(sys.argv[0])
 DART_ROOT = os.path.realpath(os.path.join(SCRIPT_DIR, '..'))
 
 usage = """\
 usage: %%prog [options] [targets]
 
-This script runs 'make' in the *current* directory. So, run it from
-the Dart repo root,
-
-  %s ,
-
-unless you really intend to use a non-default Makefile.""" % DART_ROOT
+This script invokes ninja to build Dart.
+"""
 
 
 def BuildOptions():
   result = optparse.OptionParser(usage=usage)
   result.add_option("-m", "--mode",
       help='Build variants (comma-separated).',
       metavar='[all,debug,release,product]',
       default='debug')
   result.add_option("-v", "--verbose",
       help='Verbose output.',
@@ skipping 269 matching lines @@
     if r != 0:
       return 1
 
   endtime = time.time()
   print ("The build took %.3f seconds" % (endtime - starttime))
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(Main())