Compiled languages are Meson's bread and butter, but hardly required.
This is convenient, because many test caases specifically, do not care
about testing the compiler interactions.
In such cases, we can skip doing compiler lookups which aren't used, as
they only slow down test setup.
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
If gtest is patched to have a pkg-config file, that will report the
version, so force the 'system' method to be used when we are exercising
that an unknown version doesn't satisfy any version constraint.
Jussi Pakkanen
Eli Schwartz
Dylan Baker
Jon Turney