In most places, we now refer to "builddir/" which is a lot less likely
to make people think it is a subcommand which needs to be used
literally.
This is a regression since commit 276d342eba
due to the existence of new docs which were added later on, using the
wrong form.
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
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.