See tools/clang/scripts/update.sh. This'll be used to run ASan on the bots.

BUG=469928

Change-Id: I6b5093c2db21ad4ed742852944e77a6b32e29e29
Reviewed-on: https://boringssl-review.googlesource.com/4402
Reviewed-by: Adam Langley <agl@google.com>

- Pull in a trimmed down version of vs_toolchain.py from Chromium.

- Drop in toolchain_vs2013.hash from Chromium to use Chromium's
  current toolchain.

- Add a very hacky vs_env.py to pull in Visual Studio. This is
  loosely based off a handful of lines of Chromium's
  tools/clang/scripts/update.py. This (and vs_toolchain.py) depends
  on gyp which is now pulled in via DEPS.

BUG=430237

Change-Id: Ic29cbb15e19a99616cfe778d0778b9a71c45338a
Reviewed-on: https://boringssl-review.googlesource.com/3900
Reviewed-by: Adam Langley <agl@google.com>

These are upstream's prebuilt binaries of:
e9493171de  cmake-3.1.3-win32-x86.zip
ab6e7aee6a  strawberry-perl-5.20.2.1-32bit-portable.zip
4c4d195118  yasm-1.2.0-win32.exe

This is intentionally using yasm 1.2.0 rather than the latest 1.3.0 to match
Chromium's current bundled version. Chromium has additional patches, but they
all seem to be either in 1.2.0 or not relevant for us.

Also update extract.py a little to account for these.

BUG=430237

Change-Id: Iad6687e493900b25390d99882c7ceea62fff8b9b
Reviewed-on: https://boringssl-review.googlesource.com/3710
Reviewed-by: Adam Langley <agl@google.com>

Built from:
45f4d3fa8a2f61cc092ae461aac4cac1bab4ac6706f98274ea7f314dd315c6d0  cmake-3.1.3.tar.gz

We're still waiting on infra before the buildbot master is up, but let's get
this ready for when we do; it should be fairly easy.

BUG=430237

Change-Id: I3a414743d44052e1aa48759fa5f125db4d4913b5
Reviewed-on: https://boringssl-review.googlesource.com/3670
Reviewed-by: Adam Langley <agl@google.com>

Built from:
45f4d3fa8a2f61cc092ae461aac4cac1bab4ac6706f98274ea7f314dd315c6d0  cmake-3.1.3.tar.gz

Also drop in an extraction script.

Change-Id: I3487e9d432290a7dbabf854b927412c58c35d12b
Reviewed-on: https://boringssl-review.googlesource.com/3492
Reviewed-by: Adam Langley <agl@google.com>