exclude SkJumper_stages_8bit.cpp from Google3 build

Like _lowp.cpp, it's only meant to be compiled offline.

Change-Id: I0d4f7c1fd8fa880ffd084c1e332f6a33def6e26f
Reviewed-on: https://skia-review.googlesource.com/30262
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Mike Klein <mtklein@chromium.org>
1 file changed