Bug#1041537: python3 platlib points again to /usr/local

[Jeremy Bícha]

Control: found 1041537 1.1.1-2

I believe meson in Testing also has this issue.

We have been working around this in several Debian packages by setting
this in debian/rules:
export DEB_PYTHON_INSTALL_LAYOUT = deb

Thank you,
Jeremy Bícha