Rebuilding a package after removing a build step

[Konrad Hinsen]

Hi everyone,

Until today, I thought that all parts of a package definition that could
make a difference to the outputs enter somehow into the package hash,
such that any relevant change to a package definition causes a rebuild.

Today's experience: I built a package, then removed an "add-after" form
from "modify-phases", effectively removing a build step, and ran "guix
build" again. It built nothing, and returned the same path (same hash)
as before.

Is this a bug or a feature? If it's a feature, how do I get Guix to
rebuild the package after removing a build step?

Cheers,
  Konrad.