The bionic image is really old and mainly exists to test that Meson
itself still works on really old distros (and really old python).
Ideally we'd avoid depending too much on it.
We can get a very modern pypy3 automatically this way, and potentially
use it for more stuff too.
The pip package is for python 3.6, but installs pip for all versions of
python. Apparently. Including python 3.7.
So do all other packages, especially the ones where it doesn't work but
pip thinks it is installed anyway. Force a reinstall.
D lang compilers have an option -release (or similar) which turns off
asserts, contracts, and other runtime type checking. This patch wires
that up to the b_ndebug flag.
Fixes#7082
Eli Schwartz
mattip
Matthias Klumpp
Daniel Mensinger
Cary Converse
Dylan Baker