/usr/lib/tk8.6/tkConfig.sh is in tk8.6-dev 8.6.5-1.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
1 2
#! /bin/sh . /usr/lib/`dpkg-architecture -qDEB_HOST_MULTIARCH`/tk8.6/tkConfig.sh