preinst is in pkg-create-dbgsym 0.67~trusty.
This file is a maintainer script. It is executed when installing (*inst) or removing (*rm) the package.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 | #! /bin/sh
set -e
case "$1" in
    install|upgrade)
	dpkg-divert --add --rename --package pkg-create-dbgsym --divert /usr/bin/dh_strip.pkg-create-dbgsym /usr/bin/dh_strip > /dev/null
	dpkg-divert --add --rename --package pkg-create-dbgsym --divert /usr/bin/dh_gencontrol.pkg-create-dbgsym /usr/bin/dh_gencontrol > /dev/null
	;;
    abort-upgrade)
	;;
    *)
	echo "postinst called with unknown argument \`$1'" >&2
	exit 0
	;;
esac
exit 0
 |