Update CMake to suppress struct initialization warning on MSVC

Change-Id: I30258b48bc6f216e7afd516ffce6eca8a8e84ca6
Reviewed-on: https://skia-review.googlesource.com/121585
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
1 file changed