valac 0.56..16 exposes C level warnings for generated code
When the attached project is compiled with valac 0.56.15 or earlier, no C warnings are generated for the transpiled vala code.
With 0.56.16 (via Arch testing), numerous C warnings are generated from the vala code.
I'm not sure you wish to expose these, nor require (user project) complex meson settings to suppress them.