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
* gtkdoc: Add 'check' kwarg
This runs gtkdoc-check in meson tests.
Also reorganize the gtkdoc test because we cannot reliably build
multiple doc into the same directory. Not all files generated by gtk-doc
are prefixed with the target name.
The GtkDoc test has been extended to also test the inclusion of
generated files.
To test this, a new python script has been included which generates
a new docbook file which is included as content file.