this bug is similar to #1063629 in that it removes another use of "uname -s"
from maintainer scripts so that it will become possible to create chroots of a
foreign kernel using dpkg --force-script chroootless. In contrast to the other
bug, the solution I propose in this bug uses a non-empty DPKG_ROOT as an
indicator not to call "uname -s". The patch can be found here: