postinst is in libmirclientplatform-android 0.1.8+14.04.20140411-0ubuntu1.
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 | #!/bin/sh
set -e
if [ "$1" = "configure" ];
then
    update-alternatives --force --install \
        /etc/ld.so.conf.d/x86_64-linux-gnu_mirclientplatform.conf \
        x86_64-linux-gnu_mirclientplatform_conf \
        /usr/lib/x86_64-linux-gnu/mir/clientplatform/android/ld.so.conf \
        500
    LDCONFIG_NOTRIGGER=y ldconfig
fi
exit 0
 |