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 test covers the case where the resource script references a file which
is created by a custom_target (in this case, an icon).
Put icon in a separate directory to ensure we excercise setting the include
path to the directory which contains it.
Expose depend_files: from the custom_target this creates.
This is the change suggested in #2815, with tests and documentation added.
Fixes#2789 (duplicate #2830)