Fix sk_app macOS raster window build conditions.

The "raster" window on macOS is actually backed by GL. Fix the build
rules and code conditions to reflect this. This allows for some sk_app
applications to run on macOS with skia_use_gl=false.

Change-Id: I5d7b37c4172079e163690faa4e55a622a6d4f844
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/397256
Commit-Queue: Ben Wagner <bungeman@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
4 files changed