move SK_ENABLE_DISCRETE_GPU to cover only tools

Change-Id: I390bd2cfae16651cf109c91b1047caf235cd6df4
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/210033
Commit-Queue: Mike Klein <mtklein@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Auto-Submit: Mike Klein <mtklein@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
1 file changed