Add test to check against sharpening optimization

After b/214850438 we took a second look at the sharpening optimization.
While it seems doable, it is not straightforward. We are adding a
comment and a test to make sure we are not mistakenly enabling it.

Test: art/test/testrunner/testrunner.py --host --64 --optimizing -b
Bug: 214850438
Bug: 154012332
Change-Id: Ic619934cdd4cd322a31afce60b9becbfa4338e81
3 files changed