Patches the IncOptions so that .
Patches the IncOptions so that .tasty and .hasTasty files are pruned as needed.
This code is adapted from scalaJSPatchIncOptions in Scala.js, which needs
to do the exact same thing but for classfiles.
This complicated logic patches the ClassfileManager factory of the given IncOptions with one that is aware of .tasty and .hasTasty files emitted by the Dotty compiler. This makes sure that, when a .class file must be deleted, the corresponding .tasty or .hasTasty file is also deleted.