[gm] Make GPU backend dependency conditional on SK_GANESH constant.

Bug: skia:14227
Change-Id: I39f1d8523fb1c0664eae22f472bcf17c930a42c1
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/712896
Reviewed-by: Kevin Lubick <kjlubick@google.com>
Reviewed-by: Leandro Lovisolo <lovisolo@google.com>
Auto-Submit: Leandro Lovisolo <lovisolo@google.com>
Commit-Queue: Leandro Lovisolo <lovisolo@google.com>
2 files changed