Update to newest win_toolchain and clang_win

Bug: skia:
Change-Id: Ifb1b3bcce18630c6dd05fb45399fdae7c2a2243e
Reviewed-on: https://skia-review.googlesource.com/c/176978
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
3 files changed