Add OpenCL build.

Bug: skia:8081
Change-Id: I8b2a88cc25970398511aa078d456ca8a1182792b
Reviewed-on: https://skia-review.googlesource.com/136594
Commit-Queue: Mike Klein <mtklein@google.com>
Auto-Submit: Ben Wagner <benjaminwagner@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
19 files changed