Bug#59613: Preinst uses bashims

[Matt Ryan <matt@banana.org.uk>]

Package: libc6
Version: 2.1.3-5

The preinst script uses BASH constructs even though it's only calling /bin/sh.
This means errors are output if /bin/sh points to another shell (in my case
ash):

Preparing to replace libc6 2.1.3-2 (using .../libc6_2.1.3-5_i386.deb) ...
dirname: too many arguments
Try `dirname --help' for more information.
pushd: not found
basename: too many arguments
Try `basename --help' for more information.
popd: not found
Unpacking replacement libc6 ...


Matt.