Revert "overrideDerivation: Simplify"

This reverts commit 6640000cb7148ba39bbdcca8e0cd7f5c224bce57, which
caused passthru attributes not to be passed correctly after calling
overrideDerivation.  E.g. in the evaluation of the Nix jobset:

at `deb_ubuntu1004i386' [officialRelease = false, nix = ...]:
attribute `fullName' missing