If glibc is installed in chrootless mode (i.e. $DPKG_ROOT is not empty), then checking the currently running kernel is not useful. At the point where the chroot is created on system X, the kernel running on X can be wildly different from the system Y that the chroot is supposed to run on.

This was discovered when creating hurd chroots on linux. The tools creating the chroot have no information about the kernel which might run on the system that the chroot is built for.

This commits adds an additional condition to the preinst block doing the kernel checks. It is only executed if $DPKG_ROOT is empty, in other words, only if this is a normal installation.

Closes: #1063624