Dawn: fix MSC build.

Only pass -Wno-microsoft-cast for clang.

Change-Id: I10b610784bbbcfb397f5249f5050f1d1b0a0b69c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/293345
Reviewed-by: Weston Tracey <westont@google.com>
Commit-Queue: Stephen White <senorblanco@chromium.org>
1 file changed