wraps from subprojects are now merged into the list of wraps from main
project, so they can be used to download dependencies of dependencies
instead of having to promote wraps manually. If multiple projects
provides the same wrap file, the first one to be configured wins.
This also fix usage of sub-subproject that don't have wrap files. We can
now configure B when its source tree is at
`subprojects/A/subprojects/B/`. This has the implication that we cannot
assume that subproject "foo" is at `self.subproject_dir / 'foo'` any
more.
The value for that key must be a coma separated list of dependecy names
provided by that subproject, when no variable name is needed because the
subproject uses override_dependency().
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
Similar to meson.override_find_program() but overrides the result of the
dependency() function.
Also ensure that dependency() always returns the same result when
looking for the same dependency, this fixes cases where parts of the
project could be using a system library and other parts use the library
provided by a subproject.