I cannot talk for all distress but in Gentoo (and I believe at least arch) I
build everything
as system packages. Which means that some have to be a particular version or
include specific
patches.
The sagemath library - the python stuff - is then built and installed as a
regular python package.
We are now able to build sage on void linux by using ./bootstrap,
./configure and make; everything is installed in some local folder,
since make install is a no-op.
Trying to package it, using as many system packages as possible, and
taking advantage of its build and configure features,
is it
