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
On Deban, and assuming now on Ubuntu as well, pip3 is only available after installing the python3-pip package. For that case explicitly specified the package during the system installation.
This allows us to more easily have the documentation in sync with
the source code as people will have to document new features etc
right at the time where they implement it.