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 is a simple test case, checking for installed_files.txt, which just
makes sure the syntax is accepted.
Manual tests confirmed the permissions were set correctly.
A follow up commit adds a unit test based on this directory.