Moreover, my first experience building alire itself suggests that the
"normal" way for alire projects is to duplicate and recompile sources of
libraries, for each use of said libraries.
This is correct, because each user of said dependencies might configure them differently by using environment or project variables, so a sandbox per project is the obvious simplest approach, and now some users want it for safekeeping of self-contained build environments across many versions of a product. That said, improvements in this area are in our plan for the current development cycle.
I hope I am wrong because
alire might be or become a powerful tool to produce more Debian binary
packages from upstream sources, *if* it supports precompiled libraries.
Alire can use precompiled libraries via so-called externals. There are a number of them for Debian's and other distros' binary packages.
The fact that Ada libraries in Debian (and I guess other distros, but I'm only familiar with Debian and Ubuntu) require the use of the system GNAT was taken into account since the beginning precisely not to lose access to system libraries. It's a bit in conflict with the modus operandi of a source PM, but to me the extra complexity is worth it.
Cheers,
Álex.
--
Ludovic Brenta.