Switching cygwin setup_mount project to use bare command line.

Otherwise you're assuming you have cygwin in order to set it up.

Review URL: http://codereview.chromium.org/113505

git-svn-id: http://src.chromium.org/svn/trunk/src/build@16246 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

win/system.gyp

@@ -13,6 +13,7 @@
       'actions': [
         {
           'action_name': 'setup_mount',
+          'msvs_cygwin_shell': 0,
           'inputs': [
             '../../third_party/cygwin/setup_mount.bat',
           ],