Bug#942735: rules snippet to move the include directory is not valid shell script and breaks with Python 3.8

[Matthias Klose]

Package: src:python-persistent
Version: 4.2.2-3
Severity: serious
Tags: sid bullseye
User: debian-pyt...@lists.debian.org
Usertags: python3.8

this doesn't do what is intended, and will break with 3.8.

[...]
override_dh_install:
        dh_install
        for d in debian/python3-persistent/usr/include/python*; do \
                [ "$$d" = *m ] || mv "$$d" "$$d"m; \
        done