add guard for fuchsia build

Bug: skia:
Change-Id: I3d4ae7c3dbae63001b2fab02d0f153390973f211
Reviewed-on: https://skia-review.googlesource.com/c/170345
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
2 files changed