The code generation rules are explicitly built for each supported API
target, but they ought to be refactored since they are pretty much
identical.
In order to do that, we can store the arguments to the custom_target
rules inside an array and then iterate over each element.
This cuts down the complexity of the Meson build, and the chances of
getting something wrong due to duplication.
Emmanuele Bassi
3eaddbef62