The old win_toolchain script required a Chromium checkout, and
extracted portions of the win_toolchain from that to build the
Skia asset. Instead, use the depot_tools script that assembles
a toolchain from a locally installed MSVC.
The create script doesn't do that, but relies on the user to
run that script first. Automating everything would be a nice
follow-up.
With the new strategy, the toolchain directory is simpler, and
no longer contains the depot_tools kruft or extra directories.
Adjust the bot scripts accordingly. (Renaming the directory to
win_toolchain from 't' would be a nice touch, too).
Finally, I built the new toolchain with the updated process,
and included the ARM64 compiler and libraries, so we can set
up a bot to build Windows ARM64.
Docs-Preview: https://skia.org/?cl=176968
Bug: skia:8569
Change-Id: I4bdf3cfb29d50f4464853445d0226241e70c33b4
Reviewed-on: https://skia-review.googlesource.com/c/176968
Reviewed-by: Mike Klein <mtklein@google.com>
Reviewed-by: Eric Boren <borenet@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
