Add --packages option to gen_snapshot in order to accept package map files (see https://github.com/…

runtime/tools/create_snapshot_bin.py

 #!/usr/bin/env python
 #
 # 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.
 
 """Script to create snapshot bin file."""
 
 import getopt
 import optparse
@@ skipping 27 matching lines @@
            "form is generated")
   result.add_option("--embedder_entry_points_manifest",
       action="store", type="string",
       help="input manifest with the vm entry points in a precompiled snapshot")
   result.add_option("--script",
       action="store", type="string",
       help="Dart script for which snapshot is to be generated")
   result.add_option("--package_root",
       action="store", type="string",
       help="path used to resolve package: imports.")
+  result.add_option("--packages",
+      action="store", type="string",
+      help="package config file used to reasolve package: imports.")
   result.add_option("--url_mapping",
       default=[],
       action="append",
       help=("mapping from url to file name, used when generating snapshots " +
             "E.g.: --url_mapping=fileUri,/path/to/file.dart"))
   result.add_option("-v", "--verbose",
       help='Verbose output.',
       default=False, action="store_true")
   result.add_option("--target_os",
       action="store", type="string",
@@ skipping 47 matching lines @@
 
   # Setup arguments to the snapshot generator binary.
   script_args = ["--ignore_unrecognized_flags",
                  "--error_on_bad_type",
                  "--error_on_bad_override"]
 
   # Pass along the package_root if there is one.
   if options.package_root:
     script_args.append(''.join([ "--package_root=", options.package_root]))
 
+  # Pass along the packages if there is one.
+  if options.packages:
+    script_args.append(''.join([ "--packages=", options.packages]))
+
   # First setup the vm isolate and regular isolate snapshot output filename.
   script_args.append(''.join([ "--vm_isolate_snapshot=",
                                options.vm_output_bin ]))
   script_args.append(''.join([ "--isolate_snapshot=", options.output_bin ]))
 
   # Setup the instuctions snapshot output filename
   if options.instructions_bin:
     script_args.append(''.join([ "--instructions_snapshot=",
                                  options.instructions_bin ]))
 
@@ skipping 20 matching lines @@
     return -1
 
   # Success, update timestamp file.
   CreateTimestampFile(options)
 
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(Main())