Require the GPU backend to build our internal tools

This causes builders with skia_enable_gpu set to false to stop building
DM, nanobench, etc. Next step is to remove all of the GPU shimming used
throughout those tools, and conditional code and tests.

Bug: skia:
Change-Id: I59c1c64b7e4e300c3a72a2eed9b481ed1bdf732c
Reviewed-on: https://skia-review.googlesource.com/131146
Reviewed-by: Mike Klein <mtklein@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
1 file changed