add more win/clang bots

  - add a Debug builder
  - add Debug and Release CPU testers on GCE

CQ_INCLUDE_TRYBOTS=skia.primary:Build-Win-Clang-x86_64-Debug,Test-Win2k8-Clang-GCE-CPU-AVX2-x86_64-Debug,Test-Win2k8-Clang-GCE-CPU-AVX2-x86_64-Release

Change-Id: I4f2d7309b36a532683f68fbdde9c7a9aaaa861ea
Reviewed-on: https://skia-review.googlesource.com/29023
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Mike Klein <mtklein@chromium.org>
2 files changed