One notable change is that since this C API
relies a lot on macro_rules! to be generated
we have to activate cbindgen's `expand` option,
which will use cargo-expand to expand macros.
However this means we can't call bindgen from the build.rs
as it seems to lead to a infinite-loop
(build.rs calls bindgen which calls cargo-expand which calls build.rs...)
So we call the cbindgen binary via the makefile.