Fix optimize-baselines to not move baselines from win to win-7sp0

Fix optimize-baselines to not move baselines from win to win-7sp0
https://bugs.webkit.org/show_bug.cgi?id=90312

Reviewed by Dirk Pranke.

It used to consider win-7sp0 as the common directory for all the Apple
windows ports and incorrectly move results out of win.

* Scripts/webkitpy/common/checkout/baselineoptimizer.py:
* Scripts/webkitpy/common/checkout/baselineoptimizer_unittest.py:
(BaselineOptimizerTest.test_win_does_not_drop_to_win_7sp0):
(BaselineOptimizerTest.test_common_directory_includes_root):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@121591 268f45cc-cd09-0410-ab3c-d52691b4dbfc