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The parameters to setup_toolchain changed, adding an OS parameter and a
filename for the environment file.

Additional fixes:
- Add missing base file to list of files
- vs_toolchain should output Windows paths properly escaped

Change-Id: I0e05bf34c8b603f16b901e76164e480121ed9d14
Reviewed-on: https://chromium-review.googlesource.com/1013926Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Yngve Pettersen <yngve@vivaldi.com>
Cr-Commit-Position: refs/heads/master@{#551341}