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
In qemu, minikconf generates a depfile that meson could use to
automatically reconfigure on dependency change.
Note: someone clever can perhaps find a way to express this with a
ninja rule & depfile=. I didn't manage, so I wrote a simple depfile
parser.
The same substitutions and rules as custom_target().
Also generally fix it to actually work when run in a subdir and with
anything other than absolute paths for input and output files.
We now also log a message when configuring files.
Includes tests for all this.