Performance experiment: Disable SkSL optimization in nanobench/skpbench

Change-Id: I974571e7e0e9d0170f92b970d425d9ce530e312e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/369716
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
3 files changed