Fix PATH searching for Windows.

I am TBR-ing everything today.

TBR=agable@chromium.org,hinoka@chromium.org

Review URL: https://codereview.chromium.org/232083002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@262831 0039d316-1c4b-4281-b951-d872f2087c98

git_cache.py

@@ -155,6 +155,11 @@ class Mirror(object):
       target = os.path.abspath(os.path.expanduser(target))
       if os.path.isfile(target) and os.access(target, os.X_OK):
         return target
+      if sys.platform.startswith('win'):
+        for suffix in ('.bat', '.cmd', '.exe'):
+          alt_target = target + suffix
+          if os.path.isfile(alt_target) and os.access(target, os.X_OK):
+            return alt_target
     return None
 
   @classmethod