fix build minimal_ios_mtl_skia_app

Change-Id: I9af324bec969a1f7feb84f8e5ea97b573c56694f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/260396
Commit-Queue: Hal Canary <halcanary@google.com>
Reviewed-by: Eric Boren <borenet@google.com>
3 files changed