/usr/share/doc/pbuilder/examples/D90chrootmemo is in pbuilder 0.208ubuntu1.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 | #!/bin/sh
# example file to be used with --hookdir
#
# an example to make a note that this is a chroot in /
# suggested by Turbo Fredriksson
echo "This is a chroot made by pbuilder" > /CHROOT
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