Recent versions of the 10.0.17763 SDK have rearranged the redist
directory. This change adjusts the packaging so that we can package the
SDK with and without this change. The script looks first in the
versioned directory and if that doesn't exist then it falls back to the
unversioned directory.

See also http://crrev.com/c/1371017 for the build\vs_toolchain.py
version of this change.

Change-Id: I835bf45f613a0aebb56eb1e8e63e6ffa5252edf0
Reviewed-on: https://chromium-review.googlesource.com/c/1370609Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Bruce Dawson <brucedawson@chromium.org>