By default all subprojects are installed. If --skip-subprojects is given
with no value only the main project is installed. If --skip-subprojects
is given with a value, it should be a coma separated list of subprojects
to skip and all others will be installed.
Fixes: #2550.
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