Merge branch 'PR/portability-hurd' of https://github.com/karelzak/util-linux-work

* 'PR/portability-hurd' of https://github.com/karelzak/util-linux-work:
  agetty: simplify USE_SYSTEMD ifdef in output_special_char
  agetty: introduce USE_NETLINK to separate netlink from reload
  agetty: guard netlink-related code with AGETTY_RELOAD
  libblkid: guard loop device code with __linux__ in cache
  build-sys: move shells.c to common (non-Linux) sources
  build-sys: move netlink sources from libcommon to agetty