Add docs about building with clang-cl on Windows.

No-Try: true
Docs-Preview: https://skia.org/?cl=172061
Change-Id: I509ca82707324b49e3c439c0c07a8091ceaf374c
Reviewed-on: https://skia-review.googlesource.com/c/172061
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
1 file changed