Currently (after #29701), src/setup.py determines what "distributions" to build using is_package_installed_and_updated, which inspects the installation records found in $SAGE_SPKG_INST = $SAGE_LOCAL/var/lib/sage/installed and also the information in $SAGE_PKGS = $SAGE_ROOT/build/pkgs.

Instead, we make it configurable via sage_conf, falling back to testing features.

(Note that after #30779, src/setup.py is intended to be invoked by the user for user-defined venvs, and is separate from build/pkgs/sagelib/setup.py, which is used by the Sage distribution.)

Alternative approach:

• Add an autoconf configure script for sagelib #29119 Add an autoconf configure script for sagelib

Depends on #30779

CC: @jdemeyer @antonio-rojas @kiwifb @dimpase @embray @timokau @isuruf @jhpalmieri

Component: build

Keywords: sd111

Issue created by migration from https://trac.sagemath.org/ticket/28815