OK, after a little struggling I managed to build the package (notably, g...@github.com:alire-project/alire.git requires permissions which I don't have, used https://github.com/alire-project/alire.git).
During the build I noticed that alire pulls and recompiles several libraries it depends on. This violates Debian policy; a Debian package must never duplicate another. I notice gnatcoll and xmlezout among the dependencies that are already packaged for Debian. There may be others I didn't see. Therefore, please update the packaging of alire to build-depend on these existing packages and not to recompile them from source. I have filed bug #1029448 to track the introduction of alire into Debian. A Debian bug is also a dedicated, public mailing list: in this case, 1029...@bugs.debian.org. -- Ludovic Brenta.