This should fix a problem where our vs_toolchain.py was out-of-date
with a recipe change.

See crrev.com/c/1339101 and crrev.com/c/1330185 .

Bug: angleproject:2971
Change-Id: Ic6998942bd7a9cff34c17b0f521fc3856ca3ee2f
Reviewed-on: https://chromium-review.googlesource.com/c/1341109Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>