Also make a CPU only and GPU only build (although
the latter still has a lot of CPU logic).
Bug: skia:
Change-Id: I857c2300021c2adb5344865c28e4ad3e8d332954
Reviewed-on: https://skia-review.googlesource.com/c/162022
Reviewed-by: Kevin Lubick <kjlubick@google.com>
