Cherry-pick 'Add Win Clang x86 builds.' to skqp/dev.

The tryjob Build-Win-Clang-x86-Debug is on the CQ, but the CLs to add
that tryjob and make it succeed have not yet been cherry-picked to
skqp/dev, so all CQ dry runs are failing. This CL cherry-picks the
necessary changes to skqp/dev. Also re-gen tasks.json.

Original description below.

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Add Win Clang x86 builds.

Enable /arch:SSE2 for Win x86 builds (both MSVC and Clang).

Change-Id: I0618e938b6542b60fae3947b7e0dcde22650ba54
Reviewed-On: https://skia-review.googlesource.com/56721
Commit-Queue: Ben Wagner <benjaminwagner@google.com>
Reviewed-By: Mike Klein <mtklein@google.com>
Reviewed-on: https://skia-review.googlesource.com/117086
4 files changed