This is a copy of the bindings/ada directory from plplot, with Alire and gprbuild metadata added. This package will link against your host system's libplplot. On Debian bullseye, this is as simple as apt install libplplot17. Other versions may work, I haven't tested that.
These sources were copied from git://git.code.sf.net/p/plplot/plplot commit 95bf7ebfe56154dda5fd4301a3ab7927848a7623