util-linux.postinst: avoid running uname in maintainer script for chrootless hurd support
The output of "uname -s" is potentially wrong during chrootless installations, for example when creating a hurd chroot on linux. Running uname is now avoided by a build-time check for DEB_HOST_ARCH_OS which only generates the postinst on linux.
Closes: #1063638
Edited by Johannes Schauer Marin Rodrigues