jextract cannot generate portable code (anymore)

[some-java-user-99206970363698485155 at vodafonemail.de]

> The first option is probably the simplest -- we already have many 
> "--include-XYZ" -- maybe also adding "--include-builtin=long" would be 
> ok. Although, this might create incompatibities in cases where users 
> have already saved the include list somewhere -- e.g.
>
> https://github.com/manuelbl/JavaDoesUSB/blob/main/java-does-usb/jextract/linux/gen_linux.sh
>
> E.g. currently jextract users assume that builtin types will _always_ 
> be emitted. The change described above would alter that.
>
One option to maintain backward compatibility would be to still emit the 
builtin types by default (maybe in addition to the new `..._t` types), 
and only if `--include-builtin` is explicitly specified limit the 
builtin types to those listed by that command line argument.