Fix Win64 build of Dart VM.

tools/build.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.
 #
 
 import optparse
 import os
 import re
@@ skipping 383 matching lines @@
                     '-target',
                     target,
                     '-configuration',
                     build_config,
                     'SYMROOT=%s' % os.path.abspath('xcodebuild')
                     ]
           elif HOST_OS == 'win32':
             project_file = 'dart.sln'
             if os.path.exists('dart-%s.gyp' % CurrentDirectoryBaseName()):
               project_file = 'dart-%s.sln' % CurrentDirectoryBaseName()
+            # Select a platform suffix to pass to devenv.
+            if arch == 'ia32':
+              platform_suffix = 'Win32'
+            elif arch == 'x64':
+              platform_suffix = 'x64'
+            else:
+              print 'Unsupported arch for MSVC build: %s' % arch
+              return 1
+            config_name = '%s|%s' % (build_config, platform_suffix)
             if target == 'all':
               args = [options.devenv + os.sep + options.executable,
                       '/build',
-                      build_config,
+                      config_name,
                       project_file
                      ]
             else:
               args = [options.devenv + os.sep + options.executable,
                       '/build',
-                      build_config,
+                      config_name,
                       '/project',
                       target,
                       project_file
                      ]
           else:
             make = 'make'
             if HOST_OS == 'freebsd':
               make = 'gmake'
               # work around lack of flock
               os.environ['LINK'] = '$(CXX)'
@@ skipping 40 matching lines @@
             NotifyBuildDone(build_config, success=False, start=start_time)
             return 1
           else:
             NotifyBuildDone(build_config, success=True, start=start_time)
 
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(Main())