- Exceptions raised during subproject setup were ignored.
- Allow c_stdlib in native file, was already half supported.
- Eliminate usage of subproject variable name by overriding
'<lang>_stdlib' dependency name.
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