This is required to make the various keys in the [user options] section
work the same as they do in the meson_options.txt file, where we don't
have any rules about case sensitivity.
There is some risk here. Someone may be relying on this lower by default
behavior, and this could break their machine files.
Fixes#7731
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 exposes the already existing UserStringArrayOption class through
the meson_options.txt. The intention is to provide a way for projects to
take list/array type arguments and validate that all of the elements in
that array are valid without using complex looping constructrs.