Remove msvs_cygwin_dirs

BUG=v8:4742
R=machenbach@chromium.org,jkummerow@chromium.org

Change-Id: I03e87db1536f33a67593437f8c72c33486ecdbd1
Reviewed-on: https://chromium-review.googlesource.com/474787
Commit-Queue: Loo Rong Jie <loorongjie@gmail.com>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44610}

gypfiles/standalone.gypi

@@ -855,7 +855,6 @@
           }],
         ],
         'msvs_cygwin_shell': 0,
-        'msvs_cygwin_dirs': ['<(DEPTH)/third_party/cygwin'],
         'msvs_disabled_warnings': [
           # C4091: 'typedef ': ignored on left of 'X' when no variable is
           #                    declared.