run cygwin mount setup in runhooks, and remove some references to it

ui/base/strings/ui_strings.gyp

 {
   'variables': {
     'chromium_code': 1,
     'grit_base_out_dir': '<(SHARED_INTERMEDIATE_DIR)/ui',
   },
   'targets': [
     {
       'target_name': 'ui_strings',
       'type': 'none',
       'actions': [
@@ skipping 13 matching lines @@
           },
           'includes': [ '../../../build/grit_action.gypi' ],
         },
       ],
       'direct_dependent_settings': {
         'include_dirs': [
           '<(grit_base_out_dir)/app_locale_settings',
           '<(grit_base_out_dir)/ui_strings',
         ],
       },
-      'conditions': [
-        ['OS=="win"', {
-          'dependencies': ['../../../build/win/system.gyp:cygwin'],
-        }],
-      ],
     },
   ],
   'conditions': [
     ['os_posix == 1 and OS != "mac"', {
       'targets': [{
         'target_name': 'ui_unittest_strings',
         'type': 'none',
         'variables': {
           'repack_path': '<(DEPTH)/tools/grit/grit/format/repack.py',
         },
@@ skipping 22 matching lines @@
             'destination': '<(PRODUCT_DIR)/ui_unittests_strings',
             'files': [
               '<(grit_base_out_dir)/ui_resources/ui_resources.pak',
             ],
           },
         ],
       }],
     }],
   ],
 }